WO2018028806A1

WO2018028806A1 - Gearwheel pump for a waste heat recovery system

Info

Publication number: WO2018028806A1
Application number: PCT/EP2016/077957
Authority: WO
Inventors: Guido Bredenfeld; Jakob Branczeisz; Matthias RIEDLE; Toni Jankowski
Original assignee: Robert Bosch Gmbh
Priority date: 2016-08-09
Filing date: 2016-11-17
Publication date: 2018-02-15
Also published as: WO2018028916A1; DE102016214762A1

Abstract

A gearwheel pump (1), designed in particular as a feed fluid pump (102) of a waste heat recovery system (100), having a housing (3) in which a working chamber (17) is formed, wherein a first gearwheel (4) and a second gearwheel (5) are arranged, so as to mesh with one another, in the working chamber (17). By means of the first gearwheel (4) and the second gearwheel (5), a working medium can be conveyed through the gearwheel pump (1), wherein the first gearwheel (4) is mounted rotatably on a shaft (7), and the shaft (7) is formed as a drive shaft. Furthermore, the shaft (7) of the first gearwheel (4) has a bearing arrangement outside the working chamber (17) and is sealed off with respect to the working medium.

Description

description

Gear pump for a waste heat recovery system

The invention relates to a gear pump, in particular designed as an external gear pump, in particular a feed fluid pump, which is used in a waste heat recovery system of an internal combustion engine.

State of the art

Feed fluid pumps are known in many ways from the prior art, for example as an external gear pump from the subsequently published DE 10 2015 221 338.

In DE 10 2015 221 338 an external gear pump is described with a pump housing, wherein in the pump housing, a first gear and a second gear are arranged meshing with each other. In this case, the first gear on a first shaft and the second gear on a second shaft are arranged. The radial bearing of the first shaft via a first bearing surface and the radial bearing of the second shaft via a second bearing surface. In this case, the first bearing surface and the second bearing surface are formed on a bearing goggles.

This has the advantage that the two bearing surfaces can be manufactured in very close tolerances to each other, for example with regard to their coaxiality. This leads to a high level of smoothness and thus to low wear.

When using the external gear pump as a feed fluid pump in waste heat recovery systems, as shown for example in DE 10 2015 221 338, it is necessary to use the entire gear pump against the waste heat recovery system. recovery systems used to protect aggressive media. Typically, low-viscosity media such as ethanol or cyclopentane, refrigerants or mixtures of ethanol and cyclopentane are used, which have almost no lubricating properties and therefore in conventional plain bearings no sufficiently viable lubricating film can be formed. As a result, the bearings run permanently in a mixed friction region, which leads to increased heat development in the bearing and thus faster wear. This thus influences the service life of the entire external gear pump.

Advantages of the invention

The gear pump according to the invention, in particular embodied as a feed fluid pump of a waste heat recovery system, has the advantage that it can be used in aggressive and low-viscosity media and thereby reduces wear on the bearing of the gears. This leads to a longer life of the entire gear pump.

For this purpose, the gear pump on a housing in which a working space is formed, wherein in the working space, a first gear and a second gear are arranged meshing with each other. In this case, a working fluid can be conveyed by the gear pump by means of the first gear and the second gear. The first gear is rotatably mounted on a shaft, wherein the shaft is formed as a drive shaft. According to the invention, the shaft of the first gear has a bearing outside of the working space and is sealed by the working medium.

As a result, the storage of the first wave can be protected against aggressive and low-viscosity media, since they do not come into contact with the storage. Thus, the tribological contact points which are in contact with the medium are reduced within the gear pump, whereby the sliding movements that run in the mixed friction region can be minimized. As a result, less wear and thus a longer service life of the gear wheel scored. Especially in applications for working media of a waste heat recovery system, the inventive design of the gear pump is very suitable.

In a first advantageous embodiment, a shaft seal is arranged on the shaft of the end facing the first gear, wherein the shaft seal is formed as a radial shaft seal and surrounds the shaft of the first gear. As a result, the shaft is separated from the working fluid in the working space and sealed, so that the shaft is protected from the aggressive working fluid. In a further embodiment of the invention, it is advantageously provided that the

Gear pump has a cover, wherein in the first gear facing the end of the lid at least one sealing element is arranged. Advantageously, the shaft seal cooperates with the lid, preferably with the at least one sealing element in the lid, and thus seals the bearing of the first gear against the working space and thus against the working medium. Working medium can thus not get from the working space to the storage of the first gear, whereby a reduction in wear of the gear pump is achieved.

In advantageous embodiments, the bearing of the shaft of the first gear is formed in the cover. Advantageously, the bearing of the shaft of the first gear has a separate lubrication, for example, a grease filling on. This is made possible by the separate storage outside the working space. In addition to the separate lubrication of the bearing or instead of lubrication and cooling can be used. This achieves an improvement in the hydrodynamics within the bearing. External lubrication of the bearing also reduces friction and improves temperature management within the bearing.

In a further embodiment of the invention, it is advantageously provided that the bearing of the shaft of the first gear is formed as a single or multi-row roller bearing. Advantageously, the diameter of the first gear at least approximately the same size as the diameter of the second gear. As a result, existing manufacturing processes can be used so that a cost saving is achieved.

In advantageous developments of the inventive concept, the second gear on a fixed parallel to the shaft axis, example, by a rolling or sliding bearing, rotatably mounted. As a result, the second gear is guided radially in the housing. By means of this bearing, on the one hand, the bearing dimensions can be maximized and, on the other hand, the load conditions within the bearing point can be minimized and the hydrodynamic conditions can be improved.

In a further embodiment of the invention, it is advantageously provided that the second gear cooperates with a housing inner wall formed on the housing and thereby forms a radial bearing. Thereby, the second gear can be stored without a fixed axis, whereby the number of bearings can be reduced to a minimum. This leads to a simpler manufacturing and assembly, whereby a higher cost savings is achieved.

In advantageous embodiments, axial stop plates are formed in the housing, whereby the first gear and the second gear are axially mounted on the housing in the working space.

The radial and axial bearing of the first gear and the second gear possible misalignment within the housing and relative misalignment of the first gear and the second gear are prevented from each other and ensures full functionality of the gear pump. In an advantageous embodiment of the invention, it is provided that the axial

Starting plates made of graphite or a thermoplastic material, such as PEEK (polyetheretherketone) are produced. Many plastics, in particular PEEK, are very resistant to aggressive media and at the same time have very good tribological properties. Plastics do not corrode. The life of the gear pump is thereby increased. In particular in Plastics are therefore very suitable for application to working media of a waste heat recovery system.

In an advantageous embodiment, the gear pump is designed as external gear pump. These are very cost-effective in their production and have a robust operating behavior.

Gear pumps, especially external gear pumps, are very suitable for use in waste heat recovery systems of internal combustion engines. Therefore, the gear pump according to the invention is very advantageously usable in a waste heat recovery system. The waste heat recovery system comprises a circuit carrying the working medium, wherein the circuit in the flow direction of the working medium comprises a feed fluid pump, an evaporator, an expansion machine and a condenser. The feed fluid pump is designed as a gear pump with the features described above.

In addition to the high chemical resistance, the gear pump has a robust design, a cost-effective production and also a high wear protection.

drawings

Hereinafter, embodiments of the invention will be described in more detail with reference to the accompanying drawings.

It shows in

1 shows an external gear pump known from the prior art in an exploded view, wherein only the essential areas are shown,

2 shows a detail of the mounting of the first gear of an embodiment of the gear pump according to the invention,

3 shows a radial shaft sealing ring in a sectional view, 4 shows a detail of the mounting of the first gear wheel of a further embodiment of the gear pump according to the invention with axial thrust plates,

Fig. 5 shows schematically a waste heat recovery system. Description of the embodiments

In Fig.1 a well-known from the prior art gear pump 1, designed as external gear pump, shown in an exploded view. The gear pump 1 comprises a pump housing 3, a cover 2 and a bottom flange 26. The cover 2 and the bottom flange 26 are clamped together with the interposition of the pump housing 3 by four screws 27. The pump housing 3, the cover 2 and the bottom flange 26 define a working space 17.

In the working space 17, a first gear 4 and a second gear 5 are arranged in mesh with each other. The first gear 4 is mounted on a shaft 7 and the second gear 5 on an axis parallel to the shaft 7 19. The shaft 7 serves as a drive shaft and is connected to a drive, not shown, for example, a crankshaft of an internal combustion engine. For this purpose, the shaft 7 protrudes through the bottom flange 26.

The shaft 7 and the axis 19 each protrude through their associated gear 4, 5 and are firmly connected thereto. On both sides of the gears 4, 5, the shaft 7 and the axle 19 are mounted. The bearing of the shaft 7 and the axis 19 is effected by two bearing glasses 30, 40 wherein the bearing glasses 30, 40 are arranged in the working space 17: a bearing glasses 30 is disposed adjacent to the bottom flange 26 and another bearing glasses 40 adjacent to the cover 2. The bearing glasses 30 supports the shaft 7 and the axis 19 on the drive side and the other bearing glasses 40 on the opposite side of the gears 4, 5th

The two bearing glasses 30, 40 each have a radial bearing function and a thrust bearing function, wherein the thrust bearing function of the two bearing glasses 30, 40th is directed opposite to each other. For this purpose, the bearing glasses 30 on the front side a stop surface 31 and the other bearing glasses 40 frontally another stop surface 42. Both stop surfaces 31, 42 cooperate with the gear end faces of the two gears 4, 5 together. The stop surface 31 supports both gears 4, 5 oriented in the axial direction to the bottom flange 26; the further stop surface 42 supports both gears 4, 5 oriented in the axial direction to the cover 2.

2 shows a section of an embodiment of a gear pump 1 according to the invention in the region of the gears 4, 5. Parts of the same function are provided with the same reference numerals as in Fig.l. In the embodiment of Figure 2, the gear pump 1 is designed as an external gear pump. The gears 4, 5 therefore promote a working medium along a housing inner wall 25 of the housing 3. Generally, however, it is also possible to carry out the inventive gear pump 1 as an internal gear pump.

The first gear 4 and the second gear 5 are arranged in the working space 17 within the housing 3 meshing. Accordingly, the first teeth 22 of the first gear 4 are at their respective first tooth flanks 20 in meshing engagement with the second teeth 23 of the second gear 5 at the respective second tooth flanks 21st

For the sealing of the working space 17 to the environment extends approximately annularly around the circumference of the shaft 7, a shaft seal 6, said shaft seal 6 with the lid 2, in this embodiment, with a sealing element 24 in the lid 2, cooperates. The sealing element 24 is arranged in corresponding grooves in the cover 2. As a result, the rolling bearing 8 of the shaft 7 is separated from the working medium. In addition, an external lubricant supply, such as a grease filling of the rolling bearing 8 is possible.

In order to ensure the tightness between the cover 2 and the housing 3 and thus the tightness of the gear pump 1, a housing seal 240 is arranged in the cover 2. This housing seal 240 may also be in one piece be formed with the shaft seal 24 in the lid 2. However, the sealing element 24 is not essential to the tightness between the shaft seal 6 and the cover 2 and therefore can be omitted.

The rotatable radial mounting of the second gear 5 takes place on a fixed axis 19, for example by a rolling or sliding bearing.

3 shows an embodiment of the shaft seal 6 in a sectional view. In this case, the shaft seal 6 is formed as a radial shaft seal 10, which a sealing housing 11, preferably made of metal, a dust lip 12 and a sealing lip 13, preferably of a polymer such as PTFE (polytetrafluoroethylene), FKM (fluoro rubber), NBR (nitrile rubber) or higher polymers , includes.

4 shows a section of a further embodiment of the gear pump 1 according to the invention in the region of the toothed wheels 4, 5. In the housing 3 axial stop plates 9 are formed, through which the first gear 4 and the second gear 5 via the housing 3 and the cover. 2 are stored axially in the working space 17. Here, the axial stop plates 9 made of graphite or a thermoplastic material, such as PEEK (polyetheretherketone), produced. Thus, a high wear resistance is ensured even when using aggressive working media at the bearing point.

As in FIG. 2, the mounting of the shaft 7 serving as the drive shaft is mounted externally in the cover 2 in FIG. The shaft seal 6 extends, as in Fig.2, approximately annularly around the circumference of the shaft 7, a shaft seal 6 and cooperates with the cover 2. As a result, the rolling bearing 8 of the shaft 7 is separated from the working medium. In the lid 2 also securing elements 28 are arranged for the axial bearing of the rolling bearing 8. It is also possible to use these securing elements 28 in the embodiment of the gear pump 1 in FIG. The second gear 5 is executed without own shaft bearing. To form a radial bearing, the second gear 5 cooperates with the housing inner wall 25. It accounts for more, related to conventional constructions bearings.

Due to the external support of serving as a drive shaft shaft 7, the number of bearings can be reduced to a minimum, since the bearings or the composite of drive, bearings, shaft, axle and housing seat no longer need to be aligned so exactly. The engine position can be realized solely by the part of the gear pump 1 in which the main shaft bearing, in this case the shaft 7 in the cover 2, is accommodated.

5 shows a waste heat recovery system 100 of an internal combustion engine 110. The internal combustion engine 110 is supplied with oxygen via an air supply 112; the exhaust gas emitted after the combustion process is passed through a

Exhaust pipe 111 discharged from the engine 110.

The waste heat recovery system 100 has a working medium leading circuit 100 a, which comprises in the flow direction of the working medium a feed fluid pump 102, an evaporator 103, an expansion machine 104 and a condenser 105. The working medium can be fed as needed via a branch line from a sump 101 and a valve unit 101a in the circuit 100a. The collecting container 101 may alternatively be incorporated into the circuit 100a.

The evaporator 103 is connected to the exhaust pipe 111 of the internal combustion engine 110, so uses the heat energy of the exhaust gas of the engine 110. Liquid working fluid is conveyed through the feed fluid pump 102, optionally from the reservoir 101, in the evaporator 103 and there by the heat energy of the exhaust gas Internal combustion engine 110 evaporates. The vaporized working medium is subsequently expanded in the expansion machine 104 with release of mechanical energy, for example to a generator, not shown, or to a transmission, not shown. Subsequently, will the working medium in the condenser 105 is liquefied again and returned to the collecting container 101 or fed to the feed fluid pump 102.

According to the invention, the embodiment of the gear pump 1 described above is very well suited for use as a feed fluid pump

102 within the waste heat recovery system 100, since the working medium used there is low-viscosity and very aggressive and the function of the chemical resistance for the feed fluid pump 102 is very important. Overall, the service life of the gear pump 1, 102 or of the entire waste heat recovery system 100 is thus also increased.

Claims

claims

1. gear pump (1), in particular designed as a feed fluid pump (102) of a waste heat recovery system (100), with a housing (3) in which a working space (17) is formed, wherein in the working space (17) a first gear (4) and a second gear (5) are meshed with each other, wherein by means of the first gear (4) and the second gear (5) a working fluid through the gear pump (1) is conveyed, wherein the first gear (4) on a shaft (7 ), wherein the shaft (7) is designed as a drive shaft, characterized in that the shaft (7) of the first gear (4) has a bearing outside the working space (17) and is sealed by the working medium.

2. Gear pump (1) according to claim 1, characterized in that on the shaft (7) facing the end of the first gear (4) has a shaft seal (6) is arranged, wherein the shaft seal (6) is designed as a radial shaft seal and the Surrounding shaft (7) of the first gear (4).

3. gear pump (1) according to claim 1 or 2, characterized in that the gear pump (1) has a cover (2), wherein at the said housing (3) facing the end of the lid (2) at least one sealing element (24) is.

4. gear pump (1) according to claim 3, characterized in that the shaft seal (6) with the cover (2), preferably with the at least one sealing element (24) cooperates and the bearing of the first gear (4) against the working space ( 17) and thus seals against the working fluid.

5. gear pump (1) according to claim 3 or 4, characterized in that in the cover (2), the bearing of the shaft (7) of the first gear (4) is formed.

6. gear pump (1) according to one of claims 1 to 5, characterized in that the bearing of the shaft (7) of the first gear (4) has a separate lubrication, such as a grease.

7. gear pump (1) according to one of claims 1 to 6, characterized in that the bearing of the shaft (7) of the first gear (4) is designed as a single or multi-row roller bearing.

8. Gear pump (1) according to one of claims 1 to 7, characterized in that the diameter of the first gear (4) is at least approximately the same size as the diameter of the second gear (5).

9. gear pump (1) according to one of claims 1 to 8, characterized in that the second gear (5) on a fixed parallel to the shaft (7) arranged axis (19), for example by a rolling or sliding bearing, rotatable radially is stored.

10. Gear pump (1) according to one of the preceding claims, characterized in that the second gear (5) cooperates with a housing (3) formed on the housing inner wall (25) and thereby forms a radial bearing.

11. Gear pump (1) according to claim 3, characterized in that in the housing (3) axial stop plates (9) are formed, whereby the first gear (4) and the second gear (5) via the housing (3) and the Cover (2) are axially mounted in the working space (17).

12. gear pump (1) according to claim 11, characterized in that the axial thrust plates (9) made of graphite or a thermoplastic material, such as PEEK, are produced.

13. Gear pump (1) according to one of the preceding claims, characterized in that the gear pump (1) is designed as an external gear pump.

14. waste heat recovery system (100) with a working medium leading circuit (100 a), wherein the circuit (100 a) in the flow direction of the working medium, a feed fluid pump (102), an evaporator (103), an expansion machine (104) and a capacitor (105) , characterized in that the feed fluid pump (102) is designed as a gear pump (1) according to one of the preceding claims.