WO2018153605A1

WO2018153605A1 - Gear pump for a waste heat recovery system

Info

Publication number: WO2018153605A1
Application number: PCT/EP2018/051696
Authority: WO
Inventors: Jakob Branczeisz; Frank Pohl; Tobias Korte
Original assignee: Robert Bosch Gmbh
Priority date: 2017-02-24
Filing date: 2018-01-24
Publication date: 2018-08-30
Also published as: DE102017203004A1

Abstract

The invention relates to a gear pump (1), particularly for a waste heat recovery system. Said gear pump (1) comprises a casing (2), a working chamber (6) being formed in the casing (2). A first gear (11) and a second gear (12) mesh with each other in the working chamber (6). The casing (2) comprises a bearing pin (70). The first gear (11) is rotatably mounted on the bearing pin (70) by means of a bearing (60). A shaft sealing ring (55) separates the bearing (60) from the working chamber (6) in a media-tight manner.

Description

Description title

Gear pump for a waste heat recovery system

The present invention relates to a gear pump, in particular embodied as a feed fluid pump of a waste heat recovery system

Internal combustion engine.

State of the art

Gear pumps are widely known in the art,

For example, from the published patent application DE 10 2008 042 066 AI. The known gear pump comprises a housing which limits a working space. In the working space, a first gear and a second gear are meshed with each other.

Furthermore, the basic arrangement of Speisefluidpumpen within a waste heat recovery system of an internal combustion engine is known, for example from the published patent application DE 10 2013 205 648 AI. However, the known documents disclose how the storage of the feed fluid pump with poorly lubricating media can be operated by waste heat recovery systems over a long life.

Disclosure of the invention

The gear pump according to the invention separates the storage of the gear space-saving and media-tight from the working space, so that the

Working medium does not come into contact with the bearing. This allows the bearing to be lubricated or cooled with a separate lubricant. The risk of cavitation damage in the warehouse is thereby eliminated, especially if the Gear pump is operated as a feed fluid pump in a waste heat recovery system.

For this purpose, the gear pump comprises a housing, wherein in the housing a working space is formed. In the working space, a first gear and a second gear are meshed with each other. The housing comprises a bearing pin. The first gear is rotatably supported by means of a bearing on the bearing pin. A shaft seal separates the bearing media-tight from the working space.

Thereby, the storage of the first gear is disposed within this, whereby the space of the gear pump is minimized. The media-tight separation of the bearing of the working fluid through the shaft seal allows separate lubrication and / or cooling of the bearing, for example with a lifetime lubrication. The risk of cavitation damage in the bearing due to cavitation bubbles of the working medium is due to the media density

Separation eliminated.

Advantageously, the bearing cooperates with a bearing bore formed in the first gear. The bearing bore can also be designed as a continuous bore.

In advantageous embodiments is coaxial with the first gear

Bearing bore formed a sealing surface. The shaft seal interacts with the sealing surface. Preferably, the sealing surface is an outer circumferential surface of the first gear. A contact force between the

Shaft seal and the sealing surface ensures the media-tight separation in fluidic direction to the bearing.

In alternative advantageous embodiments, the first gear is arranged on a shaft. The bearing cooperates with a bearing bore formed in the shaft. This allows gear and shaft of different

Be made of materials. The individual functional surfaces, such as the bearing bore, can therefore consist of an optimal material.

In advantageous embodiments, a sealing surface is formed coaxially to the bearing bore on the shaft. The shaft seal interacts with the sealing surface. Preferably, the sealing surface is an outer circumferential surface of the shaft. A contact force between the shaft seal and the sealing surface ensures the media-tight separation in the fluidic direction to the bearing.

In advantageous developments of the shaft seal the bearing is arranged radially surrounding. This is on the one hand a space-saving arrangement. On the other hand, thereby sealing forces and bearing forces act radially in a plane, so that no disadvantageous overturning moments can arise.

In advantageous embodiments, the bearing is designed as a rolling bearing, in particular as a needle bearing. This is a version with a small space, so that the bearing inside the shaft or inside the first gear

can be arranged.

In advantageous developments of the bearing pin is arranged on a cover of the housing. Thus, the housing is made of several parts, so that the gear pump is very easy to install. Preferably, the cover is aligned by means of centering pins to the rest of the housing, so that there is a tight tolerances of the bearing to the working space.

In advantageous embodiments, the first gear is rotatably mounted on the opposite side of the bearing by means of another bearing on a further bearing pin. Another shaft seal separates the other bearing media-tight from the work space. By the two-sided storage tilting of the shaft or the gear is avoided. The gap dimensions can thus be better adhered to, and wear is reduced. Preferably, the further bearing is designed according to one of the embodiments described above.

Advantageously, the gear pump is designed as external gear pump. This is a cheap and robust design of the gear pump.

In advantageous developments, the second gear is mounted analogously to the first gear or with a bearing in a design as described above. 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 advantageous in one

Waste heat recovery system usable. The

Waste heat recovery system comprises a working medium leading circuit, 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 good seal of the bearing against the low-viscosity working media of the waste heat recovery system. Cavitation damage in the bearings is thereby prevented. Furthermore, no dirt particles of the

Working medium entered into the warehouse, resulting in an increase in

Lifespan of the bearing leads. In addition, the bearings can be lubricated and cooled with a separate lubricant.

Brief description of the drawings

Hereinafter, embodiments of the invention below

With reference to the accompanying drawings described in more detail. It shows:

1 is an exploded view of a prior art gear pump showing only the essential portions;

2 shows a section through a gear pump of the prior art, wherein only the essential areas are shown,

Fig. 3 is a section of a portion of a gear pump according to the invention, wherein only the essential areas are shown.

Embodiments of the invention _.

In Fig.l designed as an external gear pump gear pump 1 of the prior art is shown in an exploded view. The gear pump 1 comprises a housing 2, a cover 3 and a bottom flange 4. The cover 3 and the bottom flange 4 are clamped together with the interposition of the housing 2 by four screws 5. The housing 2, the cover 3 and the bottom flange 4 define a working space 6.

In the working space 6, a first gear 11 and a second gear 12 are arranged in mesh with each other. The first gear 11 is mounted on a first shaft 21 and the second gear 12 on a first shaft 21 parallel to the second shaft 22. The first shaft 21 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 first shaft 21 protrudes through the bottom flange. 4

The two shafts 21, 22 each protrude through their associated gear 11, 12 and are firmly connected thereto. On both sides of the gears 11, 12, the shafts 21, 22 are mounted. The storage is carried out by two bearing glasses 30, 40, wherein the bearing glasses 30, 40 are arranged in the working space 6: a bearing glasses 30 is disposed adjacent to the bottom flange 4 and another bearing glasses 40 adjacent to the lid 3. In both bearing glasses 30, 40 are respectively two bushings 9 pressed. The bearing bushes 9 of the bearing glasses 30 support the two shafts 21, 22 on the drive side and the bearing bushes 9 of the other bearing glasses 40 on the opposite side of the gears 11, 12th

The four bushings 9 each have a radial bearing function. The

Axial bearing function is achieved by the two bearing glasses 30, 40: For this purpose, the bearing glasses 30 on the front side a stop surface 31 and the other

Lagerbrille 40 frontally another stop surface 42. Both stop surfaces 31, 42 cooperate with two gears 11, 12 together. The stop surface 31 supports both gears 11, 12 oriented in the axial direction to the bottom flange 4; the further stop surface 42 supports both gears 11, 12 oriented in the axial direction to the lid 3.

To seal the working space 6 to the environment, two seals are arranged on the housing 2: A seal 28 between the housing 2 and the Cover 3, and a further seal 29 between the housing 2 and the bottom flange 4. Both seals 28, 29 extend approximately annular over the circumference of the housing 28, 29 and are usually arranged in corresponding grooves.

2 shows a section in the region of the gears 11, 12 by a

External gear pump running gear pump 1. The two gears 11, 12 are within the housing 2, ie in the working space 6, respectively. The two gears 11, 12 promote the working medium along the inner wall 61 of the housing. 2

2 further shows an inlet channel 71 and an outlet channel 72 of the gear pump 1, which open into the working space 6 of the gear pump 1. In this case, the first shaft 21 in the view of FIG. 2 rotates clockwise 21a and the second shaft 22 counterclockwise 22a. Accordingly, the first teeth 13 of the first gear 11 are at their respective first tooth flanks 13a in meshing engagement with the second teeth 14 of the second gear 12 at the respective first tooth flanks 14a. Furthermore, the first teeth heads 13b of the first teeth 13 and the second teeth heads 14b of the second teeth cooperate with the inner wall 61 of the housing 2.

In the exemplary embodiment of FIG. 2, the inlet channel 71 and the outlet channel 72 are formed in the housing 2. In alternative embodiments, however, the inlet channel 71 and the outlet channel 72 may also be otherwise configured, for example formed in the lid 3 or in the bottom flange 4.

The operation of the gear pump 1 is as follows:

One of the two gears 11, 12 is driven by the corresponding shaft 21, 22, so that meshing with each other by the tooth engagement of the corresponding teeth 13, 14, the two gears 11, 12. Alternatively, the drive can also be otherwise, for example, electromechanical, done. The first gear 11 rotates clockwise 21a and the second gear 12 counterclockwise 22a. Thereby, working fluid between the gears 11, 12 and the inner wall 61 of the housing 2 from the inlet channel 71 in the

Working space 6 and then conveyed to the outlet channel 72. The

opposite direction of flow seals the tooth engagement of the _

corresponding teeth 13, 14 between the two gears 11, 12 from. Depending on the pressure applied to the outlet channel 72, the

Working medium thereby compressed in the working space 6. The gears 11, 12 and teeth 13, 14 have in addition to the function of the

Working medium from the inlet channel 71 into the outlet channel 72 also promote the function to seal the tooth chambers between the teeth 13, 14 to the inner wall 61 of the housing 2 in order to ensure the highest possible efficiency of the gear pump 1.

According to the invention, at least one shaft 21, 22 is now mounted such that the bearing is arranged in a shaft bore or gear bore and is fluidly separated from the working space 6 by means of a shaft seal. 3 shows a section of a gear pump 1 in section, wherein only the essential areas are shown. The gear pump 1 has the first gear 11 and the second gear 12, which are arranged in the working space 6 and mesh with each other. The gear pump 1 is designed in this example as an external gear pump, but may alternatively be designed as an internal gear pump.

In the first gear 11, a bearing bore 50 is formed. In the

Execution of Figure 3, the bearing bore 50 is executed consistently, but it can alternatively be designed as a blind hole. Furthermore, in the embodiment of Figure 3, the first shaft 21 and the first gear 11 are made in one piece. Alternatively, they could also be made in two parts; the

Bearing bore 50 would therefore be formed in the first shaft 21.

On the housing 2, in the embodiment of Figure 3 taken exactly on the lid 3 or the bottom flange 4, a bearing pin 70 is arranged, which has a smaller diameter than the bearing bore 50, and in the

Bearing hole 50 protrudes. In the radial direction between the bearing pin 70 and the bearing bore 50, the bearing 60 is arranged. In the embodiment of Figure 3, the bearing 60 is a radial roller bearing. Alternatively, however, the bearing 60 can also be designed as a slide bearing and continue to absorb axial forces. in the

If a slide bearing, it would also be possible that the bearing bore 50 and "

the bearing pin 70 interact directly and thereby form the bearing 60.

In the embodiment of Figure 3, the two gears 11, 12 cooperate with a stop plate 65, which in the axial direction between the lid 3 - or bottom flange 4 - and the two gears 11, 12 is positioned. The starting plate 65 thus provides an axial bearing of the two gears 11, 12 there.

On the first gear 11 - or in an alternative embodiment on the first shaft 21 - a sealing surface 51 is formed. In the embodiment of Figure 3 is the

Sealing surface 51 an outer cylindrical surface, but may alternatively be internal, or even with the bearing bore 50th

coincide. In the radial direction between the sealing surface 51 and the housing 2 - or the lid 3 or the bottom flange 4 - is a

Shaft seal 55 is arranged, the media 60 of the bearing 60 of the

Working space 6 separates. The bearing 60 can thus be lubricated with a lubricant that does not interfere with the poorly lubricating

Working medium of the gear pump 1 mixed. Between the shaft sealing ring 55 and the stop plate 65, a spacer ring 57 is positioned in the axial direction, so that the shaft seal 55 is arranged axially defined.

Analogous to the structure of the bearing 60 of the first shaft 21 and the first gear 11, the other bearings of the gear pump 1 can be constructed.

Very low-viscosity working media, such as those in

Waste heat recovery systems used have virtually no lubricating properties. Therefore, when using such, more critical

Working media in conventional plain or rolling bearings not sufficiently viable lubricating film can be formed. The bearings therefore run permanently in the mixed friction region. This leads to an increased

Heat development in the bearing, which in turn leads to faster wear and thus premature failure of the gear pump 1. The gear pump 1 according to the invention now separates the bearing 60 - or several bearings - from the working medium. As a result, for example, too an initial lubrication or lifetime lubrication - for example by a grease filling - or external lubrication of the bearing 60 possible.

The arrangement of the bearing 60 in the interior of the shaft 21, 22 or in the interior of the gear wheel 11, 12 results in the following advantages:

By the storage within the waves 21, 22 or within the

Gears 11, 12, the bearing 60 is separated from the working fluid and can thereby be lubricated separately with a more suitable lubricant.

The center distance of the two shafts 21, 22 or gears 11, 12 arranged to one another is irrelevant for the bearings 60. In contrast, a minimum distance between the two shafts 21, 22 is absolutely necessary for externally arranged bearings. This also results in an advantage in terms of the required space for the gear pump 1 space.

Tribocontact points that are in contact with the working fluid are reduced within the gear pump 1. As a result, the

Sliding movements, which run in the adverse mixed friction range can be reduced.

The operating conditions of the bearing 60 can be made ideal, for example by external lubrication and / or cooling. This improves the hydro-dynamics within the bearing 60, and the

Life of the bearing 60 increases.

By the external or initial lubrication, the friction in the bearing 60 is significantly reduced and improves the temperature balance within the bearing 60, resulting in a longer life of the bearing 60 result.

In advantageous uses, the gear pump 1 according to the invention is used in a waste heat recovery system of an internal combustion engine. The internal combustion engine is supplied with oxygen via an air supply; the exhaust gas discharged after the combustion process is discharged from the engine through an exhaust pipe.

The waste heat recovery system comprises a circuit carrying a working medium comprising, in the flow direction of the working medium, a feed fluid pump, an evaporator, an expansion machine and a condenser. The working medium can be made as needed via a spur line from a Sump and a valve unit are fed into the circuit. The collecting container can alternatively be integrated into the circulation.

The evaporator is connected to the exhaust pipe of the internal combustion engine, thus uses the heat energy of the exhaust gas of the internal combustion engine for the

Circulation of the waste heat recovery system.

Liquid working fluid is conveyed through the feed fluid pump, possibly from the reservoir into the evaporator and there through the

Heat energy of the exhaust gas of the internal combustion engine evaporates. The evaporated

Working medium is then in the expansion machine under release of mechanical energy, for example, to a generator, not shown, or to a non-illustrated transmission relaxed. Subsequently, the working medium in the condenser is liquefied again and returned to the collecting container or fed to the feed fluid pump.

Since working media, such as those used in waste heat recovery systems, e.g. Ethanol or refrigerant, have only a very low viscosity and virtually no lubricating property, when using such critical working media no sufficiently viable lubricating film in the camps

9 conventional gear pumps are formed. The contact points of conventional bearings therefore often run in the mixed friction range or even in solid friction. This can lead not only to increased friction and the resulting heat development but also to faster wear and thus to premature failure (failure) of conventional bearings.

By separating the bearings 60 of the gear pump 1 according to the invention from the working medium, the wear, damage or abrasion or

Cavitation erosion of bearings 60 reduced or completely excluded. The bearings 60 can thereby be lubricated with a more suitable, separate lubricant and also cooled.

Claims

claims

Gear pump (1), in particular for a

Waste heat recovery system, wherein the gear pump (1) comprises a housing (2), wherein in the housing (2) a working space (6) is formed, wherein in the working space (6) a first gear (11) and a second gear (12) meshing with each other, characterized in that

the housing (2) comprises a bearing pin (70), wherein the first toothed wheel (11) is rotatably mounted on the bearing pin (70) by means of a bearing (60) and wherein a shaft sealing ring (55) seals the bearing (60) from the working space (6) separates.

Gear pump (1) according to claim 1

characterized in that

the bearing (60) cooperates with a bearing bore (50) formed in the first gear (11).

Gear pump (1) according to claim 2

characterized in that

on the first gear (11) coaxial with the bearing bore (50) a

Sealing surface (51) is formed, wherein the shaft sealing ring (55) cooperates with the sealing surface (51).

Gear pump (1) according to claim 1

characterized in that

the first gear (11) is arranged on a shaft (21) and that the bearing (60) cooperates with a bearing bore (50) formed in the shaft (21).

Gear pump (1) according to claim 4

characterized in that

a sealing surface (51) is formed coaxially with the bearing bore (50) on the shaft (21), the shaft sealing ring (55) cooperating with the sealing surface (51).

6. gear pump (1) according to one of claims 3 or 5

characterized in that

the shaft sealing ring (55) is arranged radially surrounding the bearing (60).

7. gear pump (1) according to one of claims 1 to 6

characterized in that

the bearing (60) is designed as a rolling bearing, in particular as a needle bearing.

8. gear pump (1) according to one of claims 1 to 7

characterized in that

the bearing pin (70) is arranged on a cover (3) of the housing (2).

9. Gear pump (1) according to one of claims 1 to 8

characterized in that

the first gear (11) is rotatably mounted on the side opposite the bearing (60) by means of a further bearing on a further bearing pin, wherein a further shaft seal separates the further bearing media-tight from the working space (6).

10. Gear pump (1) according to one of claims 1 to 9

characterized in that

the gear pump (1) is designed as an external gear pump.

11. Gear pump (1) according to claim 10

characterized in that

the second gear (12) is mounted analogously to the first gear (11).

12. waste heat recovery system with a working medium leading circuit, wherein the circuit in the flow direction of the working medium comprises a feed fluid pump, an evaporator, an expansion machine and a condenser,

characterized in that

the feed fluid pump is designed as a gear pump (1) according to one of claims 1 to 11.