Eccentric pump, in particular feed pump for aqueous urea solutions, and feed device with an eccentric pump

Abstract

Eccentric pump, in particular a feed pump for aqueous urea solutions, with an eccentric shaft (3) which is rotatably mounted in a pump housing (8) and which drives at least one feed disc (6) arranged in an eccentric space (7), which feed disc conveys fluid in a feed chamber (16) between the outside of the feed disc (6) and the inside of an outer ring (17) from an inlet connection (31) to an outlet connection (32), wherein the feed chamber (16) is delimited laterally by an elastic sealing disc (21) arranged in a compensation space (20) in the pump housing (8), which sealing disc is force-loaded into the sealing position, characterized in that the housing-side outer ring (17) has an elastomer layer (18) on the inside which delimits the feed chamber (16) radially outwards.

Description

[0001] The invention relates to an eccentric pump, in particular a feed pump for aqueous urea solutions, according to the preamble of claim 1 and to a feed device with such an eccentric pump according to the preamble of claim 17.

[0002] DE 10 2011 076 976 A1 describes a high-pressure pump designed as an eccentric pump. It has an eccentrically arranged pumping disc in a pump housing, which is driven by an eccentric shaft. The pumping disc runs along the annular inner wall of an eccentric chamber and encloses a crescent-shaped pumping chamber for receiving the fluid to be pumped. During a rotating movement of the pumping disc, the pumping chamber moves circumferentially from an inlet port to an outlet port, pumping the fluid to the outlet port.

[0003] Depending on the intended use, the eccentric pump is exposed to high mechanical and thermal loads and possibly to weather influences.

[0004] The invention is based on the object of creating an eccentric pump and a conveying device with simple measures which are suitable for use in a wide temperature range.

[0005] This object is achieved in the generic eccentric pump according to the invention with the characterizing features of claim 1 and in the generic conveying device according to the invention with the characterizing features of claim 17. The subclaims specify expedient further developments.

[0006] The eccentric pump according to the invention is particularly suitable for conveying small and extremely small quantities of fluid. It is preferably used as a feed pump for aqueous urea solutions, which are injected into the exhaust system for exhaust gas aftertreatment in diesel engines to reduce nitrogen oxides. The eccentric pump has a rotatably mounted and driven eccentric shaft in a pump housing, which drives the feed disc in the eccentric chamber in the pump housing. The feed disc, which has a smaller diameter than the eccentric chamber, encloses a crescent-shaped feed chamber between its outer side and the surrounding outer ring for receiving the fluid to be fed. When the eccentric shaft rotates, the feed disc moves along the inner side of the outer ring.The crescent-shaped delivery chamber rotates in the circumferential direction and moves from the inlet connection, through which the fluid enters the delivery chamber, to the outlet connection, through which the fluid is discharged from the delivery chamber.

[0007] The fluid to be pumped is, in particular, a liquid, preferably an aqueous urea solution. However, gaseous fluids, such as air, can also be pumped with the eccentric pump.

[0008] The delivery chamber is laterally delimited by the elastic sealing disc, which is located in a compensation chamber in the pump housing. The sealing disc is subjected to a pressing force into a sealed or initial position, in which the delivery chamber is sealed off from flow. Due to its elasticity, the sealing disc can deform elastically when the fluid pressure in the delivery chamber is sufficiently high, in particular in such a way that the delivery chamber is enlarged by the expansion, but the fluid remains enclosed. As soon as the pressure in the delivery chamber decreases, the sealing disc returns to its initial position.

[0009] The elasticity of the sealing disc allows for an increase in the volume of the fluid in the pumping chamber to be compensated. If, for example, the volume of a fluid increases during the transition from a liquid to a solid state due to a freezing process, the sealing disc elastically deforms into the compensation chamber in the pump housing in which the sealing disc is located. The increase in volume due to freezing of the fluid can thus be easily compensated and does not lead to component damage. If the temperature rises above freezing point, the fluid in the pumping chamber liquefies again, allowing the sealing disc to return to its original position due to the resulting volume reduction under the effect of elasticity.

[0010] According to an advantageous embodiment, at least one spring element is located in the compensation chamber, which acts on the sealing disc and presses it into the sealing or starting position. The spring element can influence the sealing force with which the sealing disc laterally delimits the delivery chamber. The elasticity of the sealing disc is determined on the one hand by its intrinsic elasticity and on the other hand by the spring force of the spring element acting on it. However, it may also be sufficient to arrange a sealing disc with no or only slight intrinsic elasticity and to let the elastic behavior be determined exclusively or largely by the spring element. In the event that no spring element is arranged in the compensation chamber, the elasticity comes exclusively from the intrinsic elasticity of the sealing disc.

[0011] A helical compression spring, for example, can be used as a spring element. Advantageously, several helical compression springs are arranged in the compensation chamber, distributed around the circumference, and these springs load the sealing disc toward its sealing position.

[0012] In an alternative design, the spring element is designed as a disc spring, which has the advantage that a uniform axial contact force acts on the sealing disc over the circumference.

[0013] The spring element(s) rest on the side facing away from the sealing disc against an inner wall of the compensation chamber. This allows the spring action of the sealing disc itself, created by the elasticity of the sealing disc, to interact with the conveying force of the spring elements.

[0014] According to an advantageous embodiment, at least one vent hole connected to the atmosphere opens into the compensation chamber. This ensures that if the fluid expands and the sealing disc deforms into the compensation chamber, the gas in the compensation chamber can escape. When the sealing disc returns to its original position, gas can flow back into the compensation chamber through the vent hole.

[0015] In an advantageous further development, the vent hole can be closed with a filter element or a steam membrane to prevent contamination.

[0016] In an alternative design, the compensation chamber has no vent hole. In this case, the gas volume enclosed in the compensation chamber acts as a gas spring, acting on the sealing disc and applying force to it into the sealing or initial position.

[0017] According to an advantageous embodiment, the sealing disc has an axially extending sealing collar that rests against a wall of the compensation chamber. The sealing collar is preferably formed integrally with the sealing disc and enables radial support on a housing-side component over a larger support surface.

[0018] Advantageously, the sealing disc is clamped between parts of the eccentric pump at its outer and / or inner circumferential edge. This allows for easy installation of the sealing disc without additional fastening parts.

[0019] The sealing collar advantageously covers a sealing ring inserted into a groove in the wall of the compensation chamber. This prevents leakage to the outside if the sealing disc is lifted off. Instead, the medium is discharged via the vent hole, which in this case forms a leakage hole. Another sealing ring can be inserted into the outer ring and covered by the disc-shaped part of the sealing disc. The sealing rings further increase the sealing effect and prevent leakage currents along the side surface of the conveyor disc or outer ring and along the inner wall of the compensation chamber.

[0020] According to an advantageous embodiment, the outer ring on the housing side, which surrounds the conveyor disc and radially delimits the conveyor chamber, has an elastomer layer on its radially inner side. During the eccentric movement, the conveyor disc is constantly in contact with the elastomer layer, which deforms at least slightly radially and simultaneously enables the conveyor disc to move circumferentially with low friction.

[0021] According to a practical design, a circumferential, concave recess is provided on the inside of the outer ring, which is covered by the elastomer layer. When contact occurs between the conveyor disc and the elastomer layer, the latter deforms radially outward and can deflect into the concave recess on the inside of the outer ring. This deflection movement serves to compensate for component tolerances. Diameter tolerances can be compensated. Since volumetric efficiency depends heavily on the leakage between the outer ring and the conveyor disc, the elastomer layer also serves as a seal. With a purely metallic seal between the outer ring and the conveyor disc, the contact surfaces and the perpendicularity must be manufactured with great precision. The elastomer layer compensates for the irregularities and tolerances in a simple and reliable manner.

[0022] According to an advantageous embodiment, the conveyor disc is provided with a radial recess on its circumferential side. At least one blocking vane is inserted into this recess, which is subjected to radially outward force. The blocking vane rests against the inner side of the outer ring or the elastomer layer on the outer ring between the inlet and outlet connections and separates the inlet connection from the outlet connection in a flow-tight manner. The blocking vane thus prevents undesired direct overflow of the fluid between the inlet and outlet connections. This ensures that the fluid fed into the conveyor chamber via the inlet connection is conveyed to the outlet connection during a conveying movement of the conveyor disc in the circumferential direction within the conveyor chamber. The blocking vane can move radially in the recess and is advantageously pressed against the inner side of the outer ring or the elastomer layer by at least one spring element.At the same time, this ensures that when the conveyor disc moves, the blocking vane can perform a wobbling movement and, with its outer end face, can perform at least a small sliding movement in the segment between the inlet and outlet connections.

[0023] In a preferred embodiment, at least one rolling bearing is located between the eccentric shaft and the conveyor disc, via which the conveyor disc sits on the eccentric shaft. The eccentric shaft has an eccentric, which supports the bearing on which the conveyor disc is arranged. When the eccentric shaft rotates, the conveyor disc executes an eccentric movement relative to the longitudinal axis of the eccentric shaft in the eccentric space. Due to the bearing, the eccentric shaft and the conveyor disc can execute a relative rotational movement to one another, so that the conveyor disc does not rotate about its own axis, but merely performs a slight wobbling movement and rolls along the inside of the outer ring or the elastomer layer.

[0024] The conveyor disc is preferably fixed to the housing via at least one positioning pin, which prevents rotation of the conveyor disc but permits the wobbling movement. The positioning pin is accommodated in a recess of the conveyor disc with sufficient play to enable the eccentric radial or wobbling movement of the conveyor disc in the eccentric space. The positioning pin protrudes through the recess and is held in housing components by projecting end sections on both sides of the conveyor disc. The recess in the conveyor disc advantageously has a width that is greater than the diameter of the positioning pin in order to enable the desired radial relative movement between the positioning pin and the conveyor disc.

[0025] It may be expedient to arrange at least one spring element between the bearing and the conveyor disc, which acts in the radial direction and supports the conveyor disc in the radial direction on the bearing. The spring element serves to compensate for manufacturing tolerances and ensures constant contact between the conveyor disc and the outer ring, thereby minimizing leakage. The eccentric pump is therefore highly efficient and ensures good repeatability of the delivery rate. The spring element can, if necessary, be designed as an elastic element, for example an elastic ring, and ensures tolerance compensation and preload towards the outer ring. In another embodiment, the spring element can also be designed as an annular spring spiral element.The spring element can also protect the eccentric pump and thus the system from hydraulic pressure peaks and overload, as the spring force must be greater than the operating pressure. Ideally, the spring force should be approximately 20% to 30% higher than the operating pressure.

[0026] It is advantageous if the conveyor disc assumes a defined starting or zero position when not driven. For this purpose, at least one locking device is provided in the eccentric chamber to hold the conveyor disc in the starting or zero position.

[0027] According to an advantageous embodiment, the eccentric shaft is provided with a component in the eccentric chamber that is connected to it in a rotationally fixed manner and assumes a specific angular position relative to the eccentric shaft. This component is part of the locking device and interacts with a locking element fixed to the housing. This allows the zero position of the eccentric pump to be defined, for example, for metering pumps. Advantageously, there is only one locking position over the 360° circumference.

[0028] Various locking means can be considered for achieving the locking position. According to an advantageous embodiment, a locking disc is arranged on the eccentric shaft, to which a locking element on the housing is assigned. The locking disc, which is preferably formed integrally with the eccentric shaft, can have a locking recess or a flattened locking area on its circumferential side. On the housing side, a locking element projects into the locking recess on the locking disc in the locking position. The locking element is, for example, a ball that is force-loaded into the locking position by a spring element. The interaction between the locking cam or locking recess and the locking element occurs in a radial direction. With a flattened locking area, this forms a locking plateau on the locking disc, on which an associated locking element that is held on the housing, e.g. a roller or a sliding block, rests in the locking position.

[0029] Designs with an interaction of the locking parts between a housing-side component and a rotating component in the axial direction—relative to the longitudinal axis of the eccentric shaft—are also possible. In this case, a locking recess is preferably located on the conveyor disc, into which a spherical locking element, for example, which is supported on a housing component, engages in the locking position.

[0030] Furthermore, the locking elements can also be designed to act magnetically in the locking position, for example as a permanent magnet and a soft-magnetic component that interacts with the permanent magnet. The permanent magnet is arranged, for example, on a locking cam on the eccentric shaft and exerts a magnetic force on the housing-side locking part, which is made of the soft-magnetic material. When the eccentric shaft rotates, the permanent magnet moves past the associated locking element on the housing component, with the magnetic force acting between these components defining the desired locking position.

[0031] According to a practical embodiment, an annular seal supported on the housing is arranged on at least one side surface of the conveyor disc. Preferably, an annular seal supported on the housing is arranged on each of the two side surfaces of the conveyor disc. The annular seal or seals ensure a flow-tight seal against any fluid escaping from the conveying chamber and prevent the fluid from flowing radially inwards towards the eccentric shaft. The annular seal is designed, for example, as a mechanical seal that rests against the side surface of the conveyor disc. In an alternative embodiment, the annular seal is designed as a diaphragm ring seal that engages in a circumferential groove on the side surface of the conveyor disc and is radially elastically compressed during the eccentric movement of the conveyor disc. The diaphragm allows the eccentric stroke of the conveyor disc without the diaphragm ring seal having to slide on the contact surfaces.This eliminates sliding friction and hysteresis effects, which would be disadvantageous for the dosing pump according to the invention.

[0032] According to a further expedient embodiment, a connecting bore is provided in the conveyor disc, extending between the side surfaces, and associated with a leakage bore in at least one adjacent housing component. Fluid that may escape from the conveying chamber and flow radially inward along the side surface of the conveyor disc can be drained via the leakage bore in the housing component. The connecting bore through the conveyor disc conveys leakage fluid from the opposite side surface of the conveyor disc to the leakage bore provided in the housing component.

[0033] According to an advantageous embodiment, a check valve is integrated into the outlet connection, which closes in the outlet direction and is opened mechanically by the conveyor disc.

[0034] The check valve serves to maintain the accumulator pressure on the pressure side of the eccentric pump, as leakage from the eccentric pump may become excessive over time. To drain the pressure side, the check valve is opened mechanically, for example, using a pin, to allow the pressure side to be drained during reverse pumping. If a check valve is not used, the eccentric pump can be operated in both directions. The pressure and suction sides are interchanged depending on the direction of rotation of the eccentric shaft.

[0035] A further aspect of the invention relates to a conveying device designed as a combination of an eccentric pump and an air pump. This combination makes it possible, for example, to introduce a portion of air into the exhaust system to reduce nitrogen oxides in addition to conveying aqueous urea solution. The eccentric pump of the conveying device is advantageously designed like the eccentric pump according to the invention.

[0036] According to a preferred embodiment, the eccentric pump and the air pump can be driven by a common drive motor. For this purpose, the eccentric shaft of the eccentric pump and a drive shaft of the air pump can be arranged coaxially and coupled via a coupling element. The eccentric shaft and drive shaft are arranged axially one behind the other, so that the drive of the eccentric shaft, for example, is also transmitted to the drive shaft or vice versa. The drive is preferably provided by an electric motor, for example, a stepper motor.

[0037] According to an advantageous embodiment, the air pump is constructed identically or largely identically to the eccentric pump. This allows two eccentric pumps to be arranged axially one behind the other and the eccentric shafts to be coupled to drive them via a common drive motor. Each pump is provided with a pump housing, and the two pump housings can preferably be connected together.

[0038] As an alternative to an eccentric pump, other designs are also possible, for example, a spiral pump with a spiral as the pumping element. In this case, the eccentric pump and the spiral pump are preferably driven by a common drive motor.

[0039] The subject matter of the application arises not only from the subject matter of the individual patent claims, but also from all information and features disclosed in the drawings and the description. Even if they are not the subject matter of the claims, they are claimed as essential to the invention insofar as they are novel, individually or in combination, over the prior art.

[0040] The invention will be explained in more detail below with reference to the exemplary embodiments shown below. Fig. 1 an axial section through an eccentric pump according to the invention, Fig. 2 to 5 each show in a radial section different phases of a conveyor disc of the eccentric pump according to the invention, Fig. 6 an axial section through the eccentric pump according to the invention in the area of a blocking vane, Fig. 7 shows in axial section one half of a further embodiment of an eccentric pump according to the invention, Fig. 8 shows in axial section one half of another embodiment of an eccentric pump according to the invention, Fig. 9 shows in axial section one half of another embodiment of an eccentric pump according to the invention, Fig. 10 in section a locking device of the eccentric pump according to Fig. 9, Fig. 11 in a representation corresponding Fig. 10 shows a further embodiment of a locking device, Fig. 12 shows in axial section one half of a further embodiment of an eccentric pump according to the invention with a further embodiment of a locking device, Fig. 13 the locking device according to Fig. 12 in a radial section, Fig. 14 shows a radial section through an eccentric pump according to the invention in a further embodiment, Fig. 15 a spring spiral element of the eccentric pump according to Fig. 14, Fig. 16 in a radial section an eccentric pump according to the invention in a further embodiment, with a check valve in the region of an outlet connection, Fig. 17 shows an enlarged section through the check valve according to Fig. 16, Fig. 18 an axial section through a conveying device with an eccentric pump-air pump combination, in which the air pump is constructed identically to the eccentric pump, Fig. 19 in a representation corresponding Fig. 18 a conveying device with an eccentric pump-air pump combination in a variant in which the air pump is designed as a spiral pump, Fig. 20 the spiral of the spiral pump according to Fig. 19 in top view.

[0041] In the figures, identical components are provided with the same reference symbols.

[0042] In Fig. 1 shows an axial section of an eccentric pump 1, which is used, for example, as a feed pump for an aqueous urea solution, which is injected into the exhaust system of a diesel internal combustion engine to reduce nitrogen oxides. The eccentric pump 1 is designed as a micro-quantity pump, pumping feed rates in the range of approximately 5 µl to approximately 100 µl (microliters). The eccentric pump 1 can, of course, also be designed for larger feed rates. The eccentric pump 1 is driven by an electric drive motor 2, which is arranged coaxially to the longitudinal axis of the eccentric pump 1 and flanged to a pump housing 8 of the eccentric pump. The drive motor 2 drives an eccentric shaft 3, which is rotatably mounted in bearings 9, 10 in the pump housing 8 and has an eccentric 4 approximately halfway along its length. A feed disk 6 is seated on the eccentric shaft with the interposition of a rolling bearing 5, preferably a ball bearing.It advantageously has the same width as the rolling bearing 5 and is located in an eccentric chamber 7 within the pump housing 8.

[0043] Any suitable motor, such as a pneumatic or hydraulic motor, can be used as drive motor 2. To pump very small volumes, drive motor 2 is advantageously a stepper motor.

[0044] The conveyor disk 6 lies between two disk-shaped rings 11, 12, against which the conveyor disk 6 rests with its side surfaces. The rings 11, 12 are axially secured by housing walls 13, 14, against whose mutually facing inner sides the rings 11, 12 rest with their mutually opposite outer sides. The housing walls 13, 14 and the rings 11, 12 are connected to one another via several screws 15 and the like distributed over the circumference. They are located at a radial distance from the conveyor disk 6, which projects radially inward beyond the rings 11, 12. The housing walls 13, 14 are each provided on their inner side with a shoulder 51, 52, on which the rings 11, 12 rest with their inner cylindrical surface 53, 54.

[0045] The rings 11, 12 and the cylindrical housing walls 13, 14 advantageously have the same outer diameter, so that the pump housing 8 has a continuously approximately smooth outer surface 55.

[0046] The bearings 9, 10, which are preferably roller bearings, are housed in recesses 56, 57 in the inner sides of the housing walls 13, 14. The recesses 56, 57 are penetrated by the eccentric shaft 3, whose Fig. 1 right end is located in the outside of the pump housing 8 or the housing wall 14.

[0047] The inner circumferential surfaces 53, 54 of the rings 11, 12 delimit the eccentric chamber 7 radially outwards, which is axially delimited by the regions of the housing walls 13, 14 projecting radially inwards beyond the rings 11, 12.

[0048] The conveyor disc 6 is surrounded at a distance by a cylindrical outer ring 17, which is covered on the inside by an elastomer layer 18. A crescent-shaped conveyor chamber 16 is formed between the conveyor disc 6 and the outer ring 17 or the elastomer layer 18. The outer ring 17 has the same outer diameter as the rings 11, 12 and the housing walls 13, 14 and the same axial width as the conveyor disc 6. The outer ring 17 rests against the two rings 11, 12 and is axially penetrated by the screws 15.

[0049] The elastomer layer 18 is elastically deformable and is radially compressed in sections as the conveyor disk rotates. On the inside of the outer ring 17 is a circumferential concave recess 19 into which the elastomer layer 18 can deform radially outward when subjected to pressure by the conveyor disk 6. The concave recess 19 on the inside of the outer ring 17 thus serves to partially accommodate the elastomer layer 18 in the event of radially outward deformation.

[0050] On the side facing the conveyor disk 6, an annular compensation chamber 20 is incorporated into the ring 12, which is open to the conveyor disk 6 and is coaxial with the eccentric shaft 3. In this compensation chamber, a sealing disk 21 is located, which is pressed against the side surface of the conveyor disk 6 by at least one spring element 22. The sealing disk 21 axially covers the conveyor chamber 16, so that the fluid in the conveyor chamber 16 is received therein in a flow-tight manner. The sealing disk 21 can elastically deform in the axial direction - relative to the longitudinal axis 23 of the pump or the eccentric shaft - into the receiving chamber 20 when the fluid in the conveyor chamber 16 experiences an increase in volume, in particular during freezing. The deformation of the sealing disc 21 into the compensation chamber 20 ensures that the components delimiting the delivery chamber 16 are not damaged when the fluid freezes and the resulting increase in volume.When the frozen fluid liquefies again, the volume increase decreases; the sealing disc 21 is then pressed back into its initial or sealing position by the spring element 22, in which the sealing disc 21 rests sealingly against the side surface of the conveyor disc 6. The compensation chamber 20 is designed to extend radially outward to the level of the outer ring 17.

[0051] In the event of hydraulic overpressure in the system, the sealing disc 21 and the compensation chamber 20 can also limit the hydraulic pressure as soon as the spring force is smaller than the hydraulic forces. Thus, the eccentric pump 1 has a built-in pressure relief valve, which advantageously improves the functional reliability of the eccentric pump 1. The dissipated overpressure can be from approximately 20% to approximately 30% above the operating pressure, i.e., the spring force is set approximately 20% to approximately 30% above the operating pressure (hydraulic pressure). Thus, during normal operation, the sealing disc 21 is not opened unintentionally. Typical operating pressures for SCR pumps are 8 to 10 bar.

[0052] The sealing disc 21 extends radially outward to the outer side 55 of the pump housing 8 and is thus axially clamped with its radially outer region between the ring 12 and the outer ring 17. An axial cylindrical sealing collar 24 is formed integrally with the sealing disc 21 and bears against the radially inner cylindrical surface 58 of the compensation chamber 20. The radially outer part of the sealing disc 21 covers a sealing ring 25, which lies in an annular groove 59 in a side surface 60 of the outer ring 17. The sealing collar 24 covers another sealing ring 26, which is accommodated in an annular groove 61 in the surface 58 in the ring 12 that radially inwardly delimits the compensation chamber 20. The two sealing rings 25, 26 prevent leakage of the fluid held in the delivery chamber 16 to the outside.

[0053] The compensation chamber 20 in the disc-shaped housing component 12 is connected to the atmosphere via at least one, preferably several, vent holes 27 distributed around its circumference. The vent holes 27 extend from the compensation chamber 20 in the axial direction and penetrate both the ring 12 and the adjoining housing wall 14. Venting of the compensation chamber 20 is possible via the vent holes 27 in the event that the sealing disc 21 elastically deforms into the compensation chamber 20 upon freezing of the fluid in the delivery chamber 16. Conversely, gas or air can flow back into the compensation chamber 20 via the vent hole 27 as soon as the sealing disc 21 returns to its original or sealing position.

[0054] The vent holes 27 can be sealed with a filter element or a vapor membrane to prevent contamination. The membrane is preferably made of Goretex.

[0055] The conveyor disk 6 is sealed against the two rings 11, 12 by a sealing ring 28, 28' each, which runs coaxially to the eccentric shaft 3. The sealing rings 28, 28' each protrude into an annular groove 62, 62' in the side surfaces 63, 63' of the rings 11, 12 and into an annular groove 64, 64' in the side surfaces 65, 65' of the conveyor disk 6. The two sealing rings 28, 28' are of identical design and have a circumferential central portion 66 from which sealing lips 67 protrude approximately radially. They bear against the side walls of the annular grooves 62, 62'; 65, 64' of the rings 11, 12 and the conveyor disk 6 under radial preload.

[0056] When the eccentric shaft 3 rotates, the conveyor disc 6 performs a wobbling motion with radial deflection within the eccentric chamber 7 with the eccentric dimension specified by the eccentric 4. In this case, the ring seals 28, which are fixedly inserted in the rings 11 and 12, are elastically deformed in the radial direction, with the sealing lips 67 ensuring tightness.

[0057] At least one leakage bore 29 is provided in the disc-shaped ring 11, extending axially to the side surface 65 of the conveyor disc 6. Distributed around the circumference, it has a plurality of connecting bores 30 that axially penetrate the conveyor disc 6. The leakage bore 29 opens into an annular channel 68, which is arranged coaxially to the eccentric shaft 3 and is provided in the side surface 63 of the ring 11. The connecting bores 30 open into the annular channel 68. A further annular channel 68' is also provided in the side surface 63' of the ring 12. The connecting bores 30 connect the two annular channels 68, 68' to one another. Leakage fluid from the delivery chamber 16, which flows radially inwards along one or both side surfaces between the delivery disc 6 and the limiting rings 11, 12, can be discharged via the connecting bore 30 or, if necessary, directly via the leakage bore 29 and returned to the tank (not shown) or to the suction connection 31.

[0058] The annular channels 68, 68' are of such a width that the connecting bores 30 are always connected to the annular channels 68, 68' during the wobbling movement of the conveyor disc 6. This allows leakage medium to be returned to the tank via the annular channels 68, 68' and the leakage bore 29 in any position of the conveyor disc 6.

[0059] In the Fig. Figures 2 to 5 show the eccentric pump 1 in radial section in various phases during one rotation of the eccentric shaft 3. The area between the conveyor disc 6 and the outer ring 17 is connected to an inlet or suction port 31 and to an outlet or pressure port 32. The medium to be pumped is introduced from a tank into the eccentric chamber in the region of the crescent-shaped pumping chamber 16 via the inlet port 31. The pressurized fluid is discharged via the outlet port 32, which is arranged at an angle to the inlet port 31.

[0060] The conveyor disc 6 has a smaller diameter than the eccentric chamber 7. With one rotation of the eccentric shaft 3, the conveyor disc 6, which sits on the cam-shaped eccentric 4 of the eccentric shaft 3, is driven in a circular orbit within the eccentric chamber 7 in a wobbling motion. In each phase, the conveyor disc 6 rests with a portion of its outer surface 69 sealingly against the elastomer layer 18. Between the outer surface 69 of the conveyor disc 6 and the elastomer layer 18 lies the crescent-shaped conveyor chamber 16, which moves in the circumferential direction as the conveyor disc 6 moves.

[0061] The conveyor disc 6 is connected to the eccentric shaft 3 via the roller bearing 5 and is prevented from rotating by a positioning pin 33. The positioning pin 33 projects through an oval recess 34 in the conveyor disc 6. The longitudinal axis of the recess 34 lies in an axial plane of the conveyor disc 6. The width of the recess 34 is slightly larger than the diameter of the positioning pin 33. This allows the delivery side 6 to reliably perform the radial or wobbling movement when the eccentric shaft 3 rotates. The sickle-shaped delivery chamber 16 moves over the circumference of the eccentric pump, as can be seen from the Fig. 2 to 5. The two ends of the positioning pin 33 are held in the rings 11, 12 ( Fig. 7 and Fig. 8). Ring 11 has a blind hole 70, and ring 12 has a through hole 71 aligned with the blind hole 70. This allows for easy installation of the positioning pin 33. The positioning pin 33 can also be firmly inserted into one of the two rings 11, 12 and be freely movable within the conveyor disc 6 by a few millimeters.

[0062] The conveyor disk 6 is provided on its circumference with a radial recess 35 into which a blocking vane 36 projects. It is loaded radially outward, preferably by at least one spring element 37, which is supported on the bottom 72 of the recess 35 and is, for example, a helical compression spring. The spring element 37 ensures that the blocking vane 36 always bears sealingly against the elastomer layer 18 with its end face. The blocking vane 36 is located between the inlet connection 31 and the outlet connection 32 and ensures a flow-tight separation between the inlet and outlet connections in all phases of the circulation of the conveyor chamber 16. The blocking vane 36 extends over the entire axial width of the conveyor disk 6 ( Fig. 6) and lies with its side edges sealingly against the side surfaces 63, 63' of the rings 11, 12.

[0063] The locking vane 36 can also be hydraulically actuated. In this case, at least one bore opens into the recess 35, through which the hydraulic pressure acts from the pressure side on the radially inner end face of the locking vane 36. It is thus pressed into its sealing position depending on the prevailing pressure.

[0064] The fluid flows through the inlet connection 31 into the delivery chamber 16 in the suction phase according to Fig. 2 fluid is pumped in the conveying phase according to Fig. 3 transported in the circumferential direction until Fig. 4 the pressure phase is reached, in which the pressure in the conveying chamber 16 is built up and, with a further movement of the conveying disc in Fig. 5 in the discharge phase, the fluid is discharged from the delivery chamber 16 via the outlet connection 32. In the position according to Fig. 5 the suction phase begins again and the entire cycle starts again.

[0065] How Fig. 6 shows, two spring elements 37 arranged axially next to one another can be provided in the recess 35 of the conveyor disc 6, which spring elements press the locking vane 36 radially outward against the elastomer layer 18. In the bottom 72 of the recess 35 there is a passage opening 73 which connects the recess 35 to the one connecting bore 30 of the conveyor disc 6 and serves as pressure equalization.

[0066] In Fig. 7 shows an embodiment of the eccentric pump 1. In this embodiment, the spring element 22, which presses the sealing disc 21 in the compensation chamber 20 against the side surface of the conveyor disc 6 and the outer ring 17, is designed as a disc spring, whereas in the embodiment according to Fig. 1, the spring element is designed as a helical compression spring. Located in the bottom 74 of the compensation chamber 20 is a recess 75 extending over the circumference of the compensation chamber 20, in which recess one of the disc springs 22 is supported by its edge. Instead of the helical compression springs 22 distributed over the circumference of the present embodiment, two disc springs arranged opposite one another are provided, which apply uniform axial load to the sealing disc 21 over its circumference.

[0067] In the previous embodiment, a recess 75 is provided for each helical compression spring 22, into which one end of the helical compression spring projects, thereby securing it in its correct position. A further difference in the embodiment according to Fig. 7 lies in the arrangement of the two sealing rings 28. They are accommodated only in the annular grooves 62, 62' of the rings 11, 12. Two of the four sealing lips 67 of the sealing rings 28, 28' rest sealingly against the side surfaces 65, 65' of the conveyor disc 6, while the other two sealing lips 67 support the sealing rings 28, 28' in the annular grooves 62, 62'. The sealing lips 67 allow reliable movement of the conveyor disc 6 during its movement.

[0068] In the embodiment according to Fig. 7, the elastomer layer on the inside of the outer ring 17 is omitted, so that the inside of the outer ring 17 directly delimits the crescent-shaped conveying chamber 16. To compensate for tolerances in its movement, the conveyor disc 6 is supported by one or more spring elements 38 in the radial direction on the ball bearing 5, which is mounted on the eccentric 4 of the eccentric shaft 3. The spring elements 38 load the conveyor disc 6 radially outwards.

[0069] In order to ensure a defined relative position of the conveyor disc 6 within the receiving eccentric chamber 7 in the initial position when the drive motor 24 is switched off, the eccentric pump 1 is provided with a locking device 76, which offers a locking position in a starting or zero position of the conveyor disc 6. The locking device 76 has a housing-side locking element 40, 41 and a locking element rotating with the eccentric shaft 3, which in the embodiment according to Fig. 7 is designed as a locking disc 39, which is advantageously formed in one piece with the eccentric shaft 3. Part of the housing-side locking element is a locking projection 40, which is arranged on the radially inner circumferential surface 54 of the ring 12 and supports a locking ball 41, which is pressed radially into a locking recess 77 on the outside of the locking disc 39 by the force of a spring element supported in the locking projection 40. The locking disc 39 has the locking recess 77 on its circumference at only one position, into which the locking ball 41 is pressed. The locking device 76 is located in the eccentric chamber 7 in the area between the conveyor disc 6 and the housing wall 14. When the eccentric shaft 3 rotates, the locking ball 41 rests against the circumference of the locking disc 39 under spring force.

[0070] In the embodiment according to Fig. 8, the locking device 76 acts in an axial instead of radial direction. The housing-side locking projection 40 is located in the transition between the housing wall 13 of the pump housing and the ring 11. The locking ball 41 is pressed axially against the side surface 65 of the conveyor disc 6 via the spring element. In the side surface 65 is the locking recess 77, into which the locking ball 41 engages in the starting or zero position of the conveyor disc 6. In contrast to the embodiment according to Fig. 7, the locking device 77 is located in the eccentric chamber 7 in the area between the conveyor disc 6 and the housing wall 13.

[0071] In the embodiments according to the Fig. 7 and Fig. 8, the locking device 76 can also be provided in the opposite part of the eccentric space 7.

[0072] In the Fig. 9 and Fig. 10 shows a further embodiment of a locking device 76, which is analogous to Fig. 7 is effective in the radial direction. The eccentric shaft 3 is provided with the locking disc 39, which has a flattened area 42 on the circumference, which defines the locking position. When the eccentric shaft 3 rotates, a locking roller 41' rests under spring force on the circumference of the locking disc 39. The locking roller 41' is provided on the radially inner end of a sliding body 78, which is displaceable in a radial guide 79. It is, for example, a sleeve that projects radially from the inner circumferential surface 54 of the ring 12 and projects into the eccentric chamber 7 in the area between the conveyor disc 6 and the housing wall 14. The sliding body 78 is provided on its end face facing the circumferential surface 54 with a centrally arranged recess 80, into which projects a compression spring 81, which is supported on the circumferential surface 54.

[0073] The locking roller 41' extends axially and has a length that corresponds approximately to the axial thickness of the locking disc 39. As Fig. As shown in Figure 10, the locking roller 41' is surrounded over part of its circumference by a half-bearing shell 82, which is fastened to the inner end face of the sliding body 78. If the guide 79 is sufficiently long, it axially overlaps the locking roller 41', so that it cannot deflect and remains in its desired position.

[0074] To ensure that the locking roller 41' is aligned in the axial direction, the guide 79 is provided with a radially extending guide slot 83 through which a pin 84 secured in the sliding body 78 protrudes. Together with the guide slot 83, it ensures that the sliding body 78 is not twisted during its sliding movement, so that the locking roller 41' is always aligned axially.

[0075] If the guide 79 and the sliding body 78 have a square cross-section or outline, the guide slot 83 and the pin 84 are not necessary.

[0076] Otherwise, the eccentric pump 1 is designed in the same way as in the embodiment according to the Fig. 7 or Fig. 8.

[0077] The embodiment according to Fig. 11 corresponds largely to that according to Fig. 10. Instead of a locking roller 41', a sliding shoe 43 is held in the radial displacement guide 79, which rests on the outer circumference of the locking disc 39. The flattened portion 42 on the circumference of the locking disc 39 also defines the locking position for the conveyor disc 6 in the locking or zero position in this exemplary embodiment. The locking disc 39 is arranged on the eccentric shaft 3 such that it defines the zero position of the eccentric pump 1 in the lower eccentric position. Otherwise, the eccentric shaft 3 would have to overcome the bottom dead center to continue rotating from the zero position.

[0078] The locking disc 39 is mounted on the eccentric shaft 3 via a roller bearing 98. As a result, the locking disc 39 is only deflected accordingly when the eccentric shaft 3 rotates. The locking device 76 presses the eccentric shaft 3 into the zero position via the eccentric position and the eccentric stroke. The roller bearing 98 keeps friction low.

[0079] In the embodiment according to the Fig. 12 and Fig. 13, the locking device 76 has the locking disc 39 on the eccentric shaft 3. A permanent magnet 44 is attached to the circumference of the locking disc 39, which preferably projects slightly beyond the circumference of the locking disc 39. The housing-side locking projection 40 is attached to the inner surface 54 of the ring 12 and projects radially inward into the eccentric space 7. The locking projection 40 consists of a soft magnetic material and interacts with the permanent magnet 44. If the permanent magnet 44 moves into a position adjacent to the locking projection 40 when the locking disc 39 is rotated, the magnetic force, which is represented by an ellipse in Fig. 13, between permanent magnet 44 and locking projection 40. Otherwise, the eccentric pump 1 is designed in the same way as in the embodiment according to the Fig. 7 or Fig. 8.

[0080] In the embodiment according to the Fig. 14 and Fig. 15, the spring element 38, which is arranged between the rolling bearing 5 and the inside of the conveyor disk 6, is designed as a spring spiral element. The spring spiral element 38 presses the conveyor disk 6 radially outward against the elastomer layer 18 on the outer ring 17, thereby compensating for tolerances in the shaft alignment and in the diameter of the conveyor disk and the outer ring. The spring spiral element 38 is preferably designed as a spring steel element. In alternative designs, rubber-elastic spring elements or elastic plastic elements are also considered for the spring element 38.

[0081] In the embodiment according to the Fig. 16 and Fig. 17, a check valve 45 is located in the pressure connection 32. It has a pin-shaped valve member 46 and a valve ball 47, which is force-loaded into a closed position of the check valve 45 by the force of a spring element 85. The valve member 46, which is slidably arranged in the check valve 45, projects into the delivery chamber 16 and is pressed radially outwards by the delivery disc 6 against the force of the spring element 85 when the delivery disc is at bottom dead center in the illustrated position of the delivery disc. The valve ball 47 is lifted off the valve seat 86 and the check valve 45 is thus opened. In this open position, a small amount of fluid can flow back into the tank. This backflow occurs by reversing the direction of rotation of the eccentric shaft 3. In the process, the pressure side is specifically emptied. The purpose of the check valve 45 is to safely store the supplied pressure on the pressure side via the pump without leakage.To protect the pressure side of the medium from freezing after the vehicle or eccentric pump 1 is shut down, it is pumped out. To ensure this "reverse pumping," the check valve 45 must be mechanically opened as described. To ensure tightness, the eccentric shaft 3 is held in the neutral position using the locking devices described above, so that the check valve 45 is closed.

[0082] During operation of the eccentric pump 1, the check valve 45 is opened by the pressure of the fluid in the crescent-shaped delivery chamber 16 and the valve member 46, so that the fluid in the delivery chamber 16 can flow out of the outlet connection 32 via the opened check valve 45. As can be seen from the sectional view according to Fig. As can be seen in Figure 17, the valve member 46 has a square basic cross-section with rounded corners, while a receptacle 87 in the check valve 45 has a circular cross-section. This creates flow channels 88 in the check valve 45, through which the fluid flows toward the valve ball 47. The spring element is designed such that the pressurized fluid lifts the valve ball 47 from the valve seat 86.

[0083] In Fig. 18 shows a conveying device with a combination of an eccentric pump 1 and an air pump 48, which is constructed identically to the eccentric pump 1. The eccentric pump 1 has a design corresponding to Fig. 1. It can also be designed according to the other embodiments. The air pump 48 serves to supply additional air during an injection process, for example, of an aqueous urea solution into the exhaust system of a diesel internal combustion engine. The eccentric pump 1 and the air pump 48 are arranged axially directly one behind the other. Their pump housings 8 lie against one another and are detachably connected to one another by screws or the like. The eccentric shafts 3 are aligned with one another and are connected to one another in a rotationally fixed manner by a coupling 49. The coupling 49 is located in through-openings 89, 90 in the adjacent housing walls 14 and 13 of the two pump housings 8.

[0084] The two eccentric shafts 3 are driven jointly by the drive motor 2.

[0085] The delivery device consists of a tandem pump, which simultaneously pumps the urea solution and air. The air is sucked in via the suction port of the air pump 48 and conveyed to the pressure port via the delivery chamber. The lines connected to the two pressure ports of the eccentric pump 1 and the air pump 48 convey the urea solution and the air into the exhaust gas stream in a suitable manner.

[0086] Depending on the application, additional pumps can be installed in the same way.

[0087] In the Fig. 19 and Fig.Figure 20 shows a conveying device with an eccentric pump 1 and an air pump 48, which, as in the previous embodiment, are arranged axially one behind the other. The eccentric shafts 3 of the pumps 1 and 48 are connected to one another in a rotationally fixed manner via the coupling 49. In this embodiment, however, the air pump 48 is not designed as an eccentric pump, but as a spiral pump and has a spiral element 50 cantilevered on one side as the conveying element. It is designed in two parts with an inner and an outer spiral element 91, 92, one of which is in a fixed position and the other is driven by the eccentric shaft 3. The inwardly decreasing radius and the concomitant reduction in the volume chamber 93 cause compression of the air, which is sucked in via an intake opening 94. This air extends axially through a disc 95 and the housing wall 14 of the spiral pump 48.The disc 95 is positively connected to the housing wall 14 in the radial direction. The spiral 50 is located between the disc 95 and another disc 96, which is designed identically to the disc 95 and arranged mirror-symmetrically to it.

[0088] The eccentric shaft 3 of the air pump 48 passes through the disc 96 and extends to the spiral element 50. Coaxial with the eccentric shaft 3 is a bore 97, which forms a pressure connection and passes through the disc 95 and the housing wall 14. The air sucked in through the intake opening 94 is conveyed by the spiral element 50 to the pressure connection 97.

[0089] The spiral 50 is surrounded by the outer ring 17, which is designed identically to the outer ring 17 of the eccentric pump 1. Since the spiral members 91, 92 roll on each other, no significant wear occurs, so the spiral pump operates without lubrication. The spiral pump generates a sufficiently high air pressure of, for example, 1 to 2 bar, which is sufficient in combination with the urea injection via the eccentric pump 1.

[0090] In another design variant, a propeller with a radial or axial fan can be used as the air pump. If higher pressures are required, a positive displacement or piston machine can also be used.

Claims

[1] Eccentric pump, in particular a feed pump for aqueous urea solutions, with an eccentric shaft (3) rotatably mounted in a pump housing (8), which drives at least one feed disc (6) arranged in an eccentric chamber (7), which feed disc conveys fluid in a feed chamber (16) between the outside of the feed disc (6) and the inside of an outer ring (17) from an inlet connection (31) to an outlet connection (32), wherein the feed chamber (16) is laterally delimited by an elastic sealing disc (21) arranged in a compensation chamber (20) in the pump housing (8), which sealing disc is subjected to force in the sealing position characterized by that the housing-side outer ring (17) has an elastomer layer (18) on the inside radially outwardly delimiting the delivery chamber (16). [2] Eccentric pump according to claim 1, characterized bythat on the inside of the outer ring (17) there is a circumferential concave recess (19) which is covered by the elastomer layer (18). [3] Eccentric pump according to claim 1 or 2, characterized by that at least one spring element (22) pressing the sealing disc (21) into the sealing position is arranged in the compensation chamber (20). [4] Eccentric pump according to one of claims 1 to 3, characterized by that at least one vent hole (27) connected to the atmosphere opens into the compensation chamber (20). [5] Eccentric pump according to one of claims 1 to 4, characterized by that the sealing disc (21) has an axial sealing collar (24) which is supported on an inner wall (58) of the compensation chamber (20). [6] Eccentric pump according to claim 5, characterized by that the sealing collar (24) covers a sealing ring (26) which is inserted into a groove (61) in the inner wall (58) of the compensation chamber (20). [7] Eccentric pump according to one of claims 1 to 6, characterized by that the sealing disc (21) covers a sealing ring (25) introduced into the outer ring (17), wherein the outer ring (17) delimits the delivery chamber (16) radially outwards. [8] Eccentric pump according to one of claims 1 to 7, characterized by in that at least one force-loaded blocking wing (36) is inserted into a radial recess (35) in the circumferential side of the conveyor disc (6), which blocking wing is located between the inlet connection (31) and the outlet connection (32) and separates them from one another in a flow-tight manner. [9] Eccentric pump according to one of claims 1 to 8, characterized by that the conveyor disc (6) is supported radially via at least one spring element (38) on a bearing (5) seated on the eccentric shaft (3). [10] Eccentric pump according to one of claims 1 to 9, characterized bythat at least one locking device (76) is accommodated in the eccentric space (7), which holds the conveyor disc (6) in a defined angular position in a locking position. [11] Eccentric pump according to one of claims 1 to 10, characterized by that the movement of the conveyor disc (6) is limited by at least one positioning pin (33) fixed to the pump housing. [12] Eccentric pump according to one of claims 1 to 11, characterized by that an annular seal (28) supported on the pump housing (8) is arranged on at least one side surface (65, 65'), preferably on both side surfaces of the conveyor disc (6). [13] Eccentric pump according to claim 12, characterized by that the ring seal (28) is designed as a mechanical seal or as a diaphragm ring seal.

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