JP2013087776A - Delivery pump for fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cool a hot bearing of a delivery pump and prevent a service life of the delivery pump from becoming dramatically short.SOLUTION: A delivery pump 1 is used to deliver fluid, and has a delivery piston 2 moveable in a delivery direction 5 from a pump inlet port 3 to a pump outlet port 4. The delivery piston 2 is supported by a bearing 6, and the bearing 6 has a cooling device 7 set to cool the bearing 6 using the fluid.

Description

  The present invention relates to a fluid delivery pump that can be used, for example, in a metering device for metering fluid from a tank into an exhaust gas treatment device for purifying exhaust gas from an internal combustion engine. Exhaust gas treatment devices that are supplied with fluid for the purpose of purifying exhaust gas are widely used, especially in the automotive industry.

  In many cases particularly in such an exhaust gas treatment apparatus, one exhaust gas purification method that is carried out is selective catalytic reduction (SCR method; SCR = selective catalytic reduction), in which nitrogen oxides in the exhaust gas are reduced. It is reduced by a reducing agent. In this case, ammonia is usually used as a reducing agent. In automobiles, ammonia is usually not stored in pure form, but in the form of a precursor fluid precursor solution that can be converted to ammonia.

  For example, an aqueous urea solution is used as the precursor solution. A 32.5% aqueous urea solution, which can be obtained under the trade name AdBlue®, is particularly often used.

  This precursor solution can then be fed to the exhaust gas in liquid form and then converted to ammonia in the exhaust gas either simply by thermal means or by hydrolysis means using a hydrolysis catalyst. It is also possible to convert the precursor solution into ammonia outside the exhaust gas in a reactor provided for this purpose.

  A delivery pump is usually required to deliver the solution from the tank to the exhaust gas treatment device or reactor. The delivery pump must make the reducing agent available to the exhaust gas treatment device for the entire time of operation of the vehicle. Thus, the delivery pump must have a very long service life. Furthermore, the delivery pump should be as cheap as possible.

  A delivery pump for the reducing agent is known, for example, from US Pat.

German Patent No. 10 2008 010 073 B4

  In view of the above as a starting point, the object of the present invention is to further alleviate the technical problems described with respect to the prior art. In particular, the present invention describes a delivery pump for fluids that is particularly suitable and further improved and particularly beneficial for delivering reducing agents.

  These objects are achieved with a delivery pump according to the features of claim 1. Further advantageous embodiments of the delivery pump are indicated in the independently expressed claims. The features individually set forth in the claims may be combined in any technically beneficial manner, and may be supplemented by exemplary matters from the detailed description, of further variations of the invention. Embodiments are obtained.

  The present invention has a delivery piston that is movable in the delivery direction from a pump inlet to a pump outlet, the delivery piston being supported in a bearing, the bearing set to cool the bearing with fluid. To a delivery pump for delivering fluid having a cooling device.

  The delivery pump is particularly suitable for delivering a reducing agent and in particular an aqueous ammonia solution as a fluid.

  The delivery pump is preferably suitable to make the fluid available at a defined pressure at the pump outlet or to achieve a defined increase in fluid pressure from the pump inlet to the pump outlet. It is suitable for. For this purpose, the delivery pump drive may be controlled by a control unit, which controls the information from at least one pressure sensor for the purpose of adjusting a defined pressure or a defined increase in pressure. Receive. The control unit can control the delivery pump drive based on information from at least one pressure sensor. The delivery pump drive is preferably a drive coil. When current flows through the drive coil, the drive coil generates an electromagnetic force that acts on the delivery piston of the delivery pump. The delivery piston can be set to operate by the force of the drive coil. The drive may also have a spring that can provide a restoring force to the delivery piston. As an example, when current flows through the drive coil, the drive coil can be set to move the delivery piston relative to the pump outlet in the delivery direction opposite the spring. If no current flows through the drive coil, and therefore the drive coil does not exert a force on the delivery piston, the spring can be set to return the delivery piston to the pump inlet opposite the delivery direction.

  The pump inlet is preferably designed to connect with an inhalation line, through which the delivery pump can draw fluid, for example from a tank. The pump outlet is preferably designed to connect with a pressure line, in which the delivery pump is for example to an exhaust gas treatment device or to an injector opening to the exhaust gas treatment device Can deliver fluid. For connection with the suction line and the pressure line, the pump inlet and the pump outlet preferably have corresponding connections to which the line can be removably connected. The delivery piston is preferably located on a common shaft with the pump inlet and pump outlet.

  The bearing preferably allows movement of the delivery piston only in the axial direction extending along the delivery direction from the pump inlet to the pump outlet. The rotation or translation of the delivery piston is preferably prevented by a bearing. The bearing is preferably a sliding bearing. The delivery piston has a piston surface and the bearing has a guide surface. The piston surface and the guide surface can slide relative to each other.

  With regard to the details of the construction of such a delivery pump, reference can now be made in particular to German Patent 10 2008 010 073 B4, which is shown in FIG. 2 and its associated description ([0039] to [0045]. Paragraph) describes the configuration in detail. FIG. 2 and the preceding paragraph are hereby incorporated by reference in their entirety.

  When the piston surface and the guide surface slide on each other in the bearing, heat is generated by friction. The cooling device is preferably set to deliver fluid to the bearing, preferably the piston and guide surfaces, to absorb heat from the bearing and, where appropriate, remove the heat. It has been found that the high temperature bearings of the delivery pump can dramatically shorten the life of the delivery pump. This is especially the case when the delivery pump is used to deliver an aqueous urea solution. At high temperatures, urea precipitates can form in aqueous urea solutions. These deposits can act like abrasive particles in delivery pumps and especially in sliding bearings and can damage the bearings and delivery pump. Thus, it is particularly beneficial for a delivery pump for delivering an aqueous urea solution to remove the heat generated in the sliding bearing. For this purpose, it is particularly beneficial to use the fluid available in the delivery pump in any case.

  A delivery pump is particularly beneficial when the cooling device is also a lubricating device for simultaneously lubricating the bearing with fluid.

  Bearings realized as sliding bearings are generally beneficial when lubricating oil is provided. Lubricating oil reduces friction between surfaces in the bearing. In the delivery pump considered here, the surface of the sliding shaft is preferably the piston surface of the delivery piston and the guide surface of the guide hole of the bearing in which the piston is guided. It is particularly preferred when a gap is created between the piston surface and the guide surface, where a lubricating film of fluid is formed.

  Due to the fact that the fluid is used simultaneously as coolant and lubricant for the delivery pump bearing, additional lubricant for the bearing may be omitted.

  The bearing is a guide channel, the delivery piston is slidably supported, and the cooling device is realized as at least one passage intersecting the guide channel, through which fluid enters the guide channel at at least one entry point. The delivery pump is particularly beneficial when invading.

  The shape of the guide channel is preferably adapted to the cross section of the delivery piston so that the delivery piston in the guide channel can move backwards and forwards in the delivery movement. The passage may be, for example, a hole, gap or slot that mates with the guide channel and thereby intersects the guide channel.

  A plurality of passages are preferably arranged along the guide channel so that the bearing or guide channel or guide surface and the piston surface can be completely wetted with fluid as much as possible. As another preferred option, the plurality of passages are also arranged around the delivery piston and guide channel in a circumferential direction to ensure complete wetting. For example, 2 to 8 passages leading to the guide channel and evenly distributed in the circumferential direction are in each case provided in 2 to 6 planes along the guide channel.

  The passage may be realized as, for example, a hole or a gap. The passage defines a connection through which fluid can move to the bearing or guide channel. This connection preferably starts from the channel and extends through the delivery pump, through which the fluid can move from the pump inlet to the pump outlet, or along that channel, the fluid is normal Flow during delivery.

  The passages described are not technically particularly complex and are an effective solution for moving fluid to the bearing.

  A delivery pump if the delivery piston has at least one recess in the region of the passage, and during the delivery movement of the delivery piston in the bearing, the recess intersects the entry point of the passage and in the process delivers fluid to the bearing Is particularly beneficial.

  The delivery piston preferably has a largely planar piston face that conforms to the shape or guide surface of the guide channel. Both the piston surface and the guide surface preferably have a low roughness, for example less than 10 μm, preferably even 5 μm. In order to reduce the friction of the delivery piston in the guide channel of the bearing, the roughness of these surfaces is low. The recess forms a re-entry area for the delivery piston relative to the piston surface. The recess can be realized as a single notch or opening in the delivery piston. The recess can also form a complete network of channels or a complete system on the piston face, allowing fluid to move through the channel, thus permitting fluid distribution across the piston face and guide face. When the recess intersects the passage, the recess region and the entry point region of the passage overlap at least partially in the overlap zone. The fluid can then enter the recess from the passage. The delivery movement changes the area of the overlapping zone. This is because the entry point and the recess move relative to each other. During the delivery movement, preferably at least sometimes there is no overlap in everything between the area of the entry point and the area of the recess. Indeed, the recess preferably intersects several different passages during the delivery movement. The flow pressures spreading in these different passages are preferably different. In this way, fluid can be effectively delivered through the bearing via the recess.

  The use of at least one recess in the delivery piston for delivering fluid to the bearing is particularly beneficial. This is because the fluid is effectively delivered to the bearing and there is no need for any additional moving parts (such as additional pumps) to deliver the fluid to the bearing.

  The delivery pump is particularly beneficial when the bearing is realized with a gap between the guide surface of the guide channel of the bearing and the piston face of the delivery piston, said gap having a gap width of at least 5 μm.

  Such a gap width between the piston surface and the guide surface is particularly beneficial to ensure that a fluid film forms in the bearing or guide channel or gap, which is particularly suitable for cooling and proper In some cases, it is also beneficial to lubricate the bearing.

  The delivery pump is particularly beneficial when the bearing is configured to provide a back flow of fluid through the bearing opposite the delivery direction of the delivery pump.

  The backflow preferably covers the entire length of the bearing. In this way, particularly effective cooling of the bearing can be achieved. It also ensures that bearing cooling is evenly distributed over the entire length of the bearing and that local overheating of the bearing does not occur.

  The delivery pump has a delivery chamber, at least one chamber injection opening opening into the delivery chamber, and at least one check valve disposed between the delivery chamber and the pump outlet in the delivery direction; A delivery pump is particularly beneficial if the delivery piston can perform a delivery motion within the delivery chamber and in that process pushes the fluid present in the delivery chamber through the check valve to the pump outlet in the delivery direction.

  During the delivery movement, the delivery piston moves periodically in and out of the delivery chamber. Thus, during the delivery movement of the delivery piston, the volume of the delivery chamber increases and decreases periodically. In a particularly beneficial variant of the delivery pump, the volume of the delivery chamber so that the minimum volume of the delivery chamber that occurs during the delivery movement is at least 10 times, preferably 20 times, particularly preferably 100 times smaller than the maximum volume of the resulting delivery chamber. A reduction is made. The opening in the delivery chamber is at least one chamber injection opening through which fluid can enter the delivery chamber in the delivery direction. Where multiple chamber injection openings are provided, they are preferably all located in a common plane aligned perpendicular to the direction of movement or axis of movement of the delivery piston. This can happen especially if the delivery piston is placed close to the position of maximum retraction during the delivery movement (ie in the direction relative to the pump inlet), where the volume of the delivery chamber is the maximum volume described Close to. During the delivery movement, the delivery piston preferably passes through at least one chamber injection opening. If the delivery piston covers the chamber injection opening, fluid cannot flow into the delivery chamber. When the delivery piston opens into the delivery chamber, fluid can flow through the chamber injection opening to the delivery chamber. There is a check valve between the delivery chamber and the pump outlet in the delivery direction. During some delivery movement in the delivery direction relative to the pump outlet, the delivery piston pushes fluid out of the delivery chamber via a check valve against the pump outlet. The check valve prevents fluid from returning from the pump outlet into the delivery chamber.

  By configuring the delivery pump in this way, it is also possible to achieve a delivery pump with a relatively high metering accuracy. The delivery pump can then be used not only as a simple delivery pump but also as a metering pump. In the case of a metering pump, the amount of fluid delivered by the delivery pump can be accurately measured. For the delivery pump described herein, the amount of fluid delivered is derived from the number of delivery strokes of the delivery piston and the volume of the delivery chamber (if the delivery piston is just covering the chamber injection opening). The delivery amount can be calculated as the product of this volume and the number of delivery strokes.

  With regard to the details of the construction of the delivery chamber of the delivery pump, reference is again made here especially to German Patent No. 10 2008 010 073 B4, which is related to FIG. 2 and the associated description ([0039] to [0045]. Paragraph) describes the construction of the delivery chamber in detail. FIG. 2 and the preceding paragraph are hereby incorporated by reference in their entirety.

  The scope of the invention is also a metering device for delivering a reducing agent from a tank into an exhaust gas treatment device, the metering device comprising a delivery line from the tank to the exhaust gas treatment device and a delivery according to the invention. And a delivery pump including a metering device disposed in the delivery line to deliver the reducing agent as a fluid from the tank to the exhaust gas treatment device.

  As explained above, the delivery pump described is particularly useful for delivering a reducing agent. Thus, it is particularly beneficial to use the delivery pump described in a metering device for the reducing agent.

  The scope of the present invention is also set in the present invention to set an internal combustion engine, an exhaust gas processing device for purifying exhaust gas from the internal combustion engine, and a reducing agent into the exhaust gas processing device. An automobile having such a weighing device.

  The present invention and related techniques are described in more detail below with reference to the drawings. The drawings show particularly preferred embodiments, but the invention is not limited thereto. In particular, the drawings shown and in particular the proportions are merely schematic.

FIG. 6 is a variation embodiment of a delivery pump. FIG. An automobile having a metering device with a delivery pump.

  FIG. 1 shows a delivery pump 1 that can deliver fluid from a pump inlet 3 to a pump outlet 4 in the delivery direction 5. For delivery, the delivery pump 1 has a delivery piston 2 that is movable backwards and forwards in a bearing 6. During this movement of the bearing 6, the delivery piston 2 performs a delivery movement 11. During the delivery movement 11, the delivery piston 2 moves regularly in and out of the delivery chamber 18. During the delivery movement 11 of the delivery piston 2, the volume of the delivery chamber 18 regularly increases and decreases. In a particularly beneficial variant of the delivery pump 1, the volume reduction is such that the minimum volume of the delivery chamber 18 that occurs during the delivery movement 11 is at least 10 times, preferably 20 times, particularly preferably the maximum volume of the delivery chamber 18 that occurs. Is made 100 times smaller. The opening in the delivery chamber 18 is at least one chamber injection opening 19 through which fluid can enter the delivery chamber 18 in the delivery direction 5. This can occur in particular when the delivery piston 2 is placed close to the position of maximum retraction during the delivery movement 11 (ie in the direction relative to the pump inlet 3), in which case the delivery chamber 18 The volume approaches the maximum volume described. During the delivery movement 11, the delivery piston 2 preferably passes through at least one chamber injection opening 19. If the delivery piston 2 covers the chamber injection opening 19, no fluid can flow into the delivery chamber 18. When the delivery piston 2 opens the delivery chamber 18, fluid can flow into the delivery chamber 18 through the chamber injection opening 19. There is a check valve 20 between the delivery chamber 18 and the pump outlet 4 in the delivery direction 5. During some delivery movement 11 in the direction relative to the pump outlet 4, the delivery piston 2 pushes fluid out of the delivery chamber 18 in the direction of the pump outlet 4 via the check valve 20. A check valve 20 prevents fluid from flowing back into the delivery chamber 18 from the pump outlet 4. The delivery movement 11 of the delivery piston 2 is at least partly achieved by the drive coil 27. Current can flow through the drive coil 27. The drive coil 27 then applies an electromagnetic force to the delivery piston 2 and moves the delivery piston 2. In addition, a spring (not shown here) may also be provided on the delivery piston 2, for example providing a restoring force against the delivery pump 2 against the direction of action of the drive coil 27.

  The bearing 6 of the delivery piston 2 is preferably realized in the form of a sliding bearing. The bearing 6 is designed as a guide channel 8 in which the delivery piston 2 is present. The guide channel 8 has a guide surface 14 and the delivery piston 2 has a piston surface 15. Since the guide surface 14 and the piston surface 15 are slidable relative to each other, it enables the delivery piston 2 to perform the delivery movement 11 in the guide channel 8 or the bearing 6. Preferably, there is a gap 13 between the piston surface 15 and the guide surface 14, which gap is at least 5 μm [micrometers], for example so that the piston surface 15 can easily slide on the guide surface 14. The gap width 16 is as follows.

  The bearing 6 has a cooling device 7. The cooling device 7 is designed to deliver the fluid delivered by the delivery pump 1 in the bearing 6 and in particular in the gap 13 between the piston surface 15 and the guide surface 14. In the variant embodiment shown here, the cooling device 7 is at least one passage 9 through which fluid can enter the bearing 6 or the guide channel 8 or the gap 13. For this purpose, the passage 9 intersects the guide channel 8. The passage 9 opens into the bearing or guide channel 8 at the entry point 12. The passage 9 is designed, for example, as a hole, notch or slot in the wall of the guide channel 8 and preferably forms a connection through which fluid can pass into the bearing 6 or the guide channel 8 or the gap 13.

  At least one recess 10 is preferably provided in the delivery piston 2. When the delivery piston 2 performs the delivery movement 11, the recess 10 is arranged to pass through the entry point 12 of the passage 9. Thus, the recess 10 facilitates and increases the delivery of fluid into the bearing 6 or guide channel 8 or gap 13. A counterflow 17 of fluid through the bearing 6 or the guide channel 8 or the gap 13 opposite the delivery direction 5 is preferably established.

  FIG. 2 shows an automobile 25 having an internal combustion engine 26 and an exhaust gas processing device 23 for purifying the exhaust gas of the internal combustion engine 26. The reducing agent can be delivered by the metering device 21 from the reducing agent tank 22 into the exhaust gas treatment device 23. The metering device further has a delivery line 24 from the tank 22 to the exhaust gas treatment device 23. A delivery pump 1 for delivering the reducing agent is provided in the delivery line 24.

DESCRIPTION OF SYMBOLS 1 Delivery pump 2 Delivery piston 3 Pump injection port 4 Pump discharge port 5 Delivery direction 6 Bearing 7 Cooling device 8 Guide channel 9 Passage 10 Recess 11 Delivery motion 12 Entry point 13 Gap 14 Guide surface 15 Piston surface 16 Gap width 17 Backflow 18 Delivery Chamber 19 Chamber injection opening 20 Check valve 21 Metering device 22 Tank 23 Exhaust gas treatment device 24 Delivery line 25 Automobile 26 Internal combustion engine 27 Drive coil

Claims (9)

  A delivery pump (1) for delivering fluid, having a delivery piston (2) movable in the delivery direction (5) from a pump inlet (3) to a pump outlet (4), said delivery piston ( 2) is supported in a bearing (6), the bearing (6) having a cooling device (7) set to cool the bearing (6) with the fluid.   The delivery pump (1) according to claim 1, wherein the cooling device (7) is also a lubricating device for simultaneously lubricating the bearing (6) with the fluid.   The bearing (6) is a guide channel (8), the delivery piston (2) is slidably supported, and the cooling device (7) has at least one passage (crossing the guide channel (8) ( Delivery pump (1) according to claim 1 or 2, realized as 9) and through the passage (9), the fluid enters the guide channel (8) at at least one entry point (12).   Said delivery piston (2) has at least one recess (10) in the region of said passage (9), said recess being between delivery movements (11) of said delivery piston (2) in said bearing (6) The delivery pump (1) of claim 3, wherein the delivery pump (1) intersects the entry point (12) of the passage (9) and in the process delivers the fluid to the bearing (6).   The bearing (6) is realized with a gap (13) between the guide surface (14) of the guide channel (8) of the bearing (6) and the piston surface (15) of the delivery piston (2). The delivery pump (1) according to any one of claims 1 to 4, wherein the gap has a gap width (16) of at least 5 μm.   The bearing (6) is set so as to obtain a backflow (17) of fluid through the bearing (6) opposite the delivery direction (5) of the delivery pump (1). A delivery pump (1) according to any one of the above.   The delivery pump (1) comprises a delivery chamber (18), at least one chamber injection opening (19) opening into the delivery chamber (18), and the delivery chamber (18) in the delivery direction (5). At least one check valve (20) disposed between the pump outlet (4) and the delivery piston (2) performing a delivery movement (11) in the delivery chamber (18) 7. In the process, fluid present in the delivery chamber (18) is pushed through the check valve (20) to the pump outlet (4) in the delivery direction (5). A delivery pump (1) according to any one of the above.   A metering device (21) for delivering a reducing agent from a tank (22) into an exhaust gas treatment device (23), wherein the metering device (21) is connected to the exhaust gas treatment device ( 23) and a delivery pump (1) according to any one of claims 1 to 7, wherein the delivery pump (1) is evacuated from the tank (22). A metering device (21) arranged in the delivery line (24) to deliver the reducing agent as a fluid to the gas treatment device (23).   An internal combustion engine (26), an exhaust gas processing device (23) for purifying exhaust gas from the internal combustion engine (26), and a setting for measuring the reducing agent into the exhaust gas processing device (23) An automobile (25) having a weighing device (21) according to claim 8.

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