WO2018134019A1

WO2018134019A1 - Motor-pump unit for a waste heat recovery system

Info

Publication number: WO2018134019A1
Application number: PCT/EP2017/083798
Authority: WO
Inventors: Guido Bredenfeld; Jakob Branczeisz; Matthias RIEDLE
Original assignee: Robert Bosch Gmbh
Priority date: 2017-01-18
Filing date: 2017-12-20
Publication date: 2018-07-26
Also published as: DE102017200708A1

Abstract

The invention relates to a motor-pump unit (80) comprising a motor (90) and a fluid pump (100). The fluid pump (100) has a pump housing (7), said pump housing (7) being equipped with an inlet and an outlet. The pump housing (7) delimits a working chamber (20). A working medium can be conveyed from the inlet to the outlet in the working chamber (20) by means of a pump device (101). The motor (90) has an output shaft (2) for transmitting a torque. The output shaft (2) is mounted in the motor (90) by means of a first shaft bearing (1a) and a second shaft bearing (1b). The pump device (101) has a drive hub (102), and the drive hub (102) is arranged on the output shaft (2).

Description

Description title

Motor-pump unit for a waste heat recovery system

The present invention relates to a motor-pump unit, in particular used as a feed fluid pump of a waste heat recovery system of an internal combustion engine.

State of the art

Fluid pumps are widely known from the prior art, for example as external gear pumps from the published patent application DE 43 09 859 A1. From EP 1 933 033 A1 a motor-pump unit is known which has a

Gear pump and an electric motor includes.

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 A1. However, the known documents often leave open, as the feed fluid pump can be operated with aggressive working fluids of waste heat recovery systems, which have a very low viscosity, with the longest possible lifetime. In particular, the bearings of such feed fluid pumps are subject to high stress. Therefore, extremely wear-resistant and correspondingly expensive materials are often used for the bearings.

Disclosure of the invention The fluid pump according to the invention has the advantage that it uses the shaft bearings of the motor driving them. Therefore she can

especially for low-viscosity, poorly lubricating working media are used, as used for example in waste heat recovery systems. As a result, the fluid pump or the entire motor-pump unit is resistant to damage caused by poor lubrication and cavitation and can thus be used for operating temperatures close to the evaporation temperature of the working fluid to be pumped. Therefore, the engine-pump unit is particularly suitable for exhaust heat recovery systems of internal combustion engines.

For this purpose, the motor-pump unit comprises a motor and a fluid pump. The fluid pump has a pump housing, wherein an inlet and an outlet are formed in the pump housing. The pump housing limits a working space. In the working space is a working medium by means of a

Conveyor from the inlet to the outlet conveyed. The engine has an output shaft for transmitting torque. The output shaft is supported in the engine by means of a first shaft bearing and by means of a second shaft bearing. The conveyor has a drive hub. The drive hub is arranged on the output shaft.

As a result, the total cost of the motor-pump unit are reduced, since virtually eliminating the cost of storage and the drive shaft of the conveyor and for the coupling between the output shaft and the drive shaft of the conveyor. Furthermore, this results in a reduction of the required installation space. In addition, by means of this arrangement, the two shaft bearings can be fluidly separated relatively comparatively easily from the working space by means of sealing arrangements, so that aggressive or poorly lubricating working media can also be used. The two shaft bearings can in advantageous developments even with a suitable

Lubricants are lubricated.

In advantageous developments, the drive hub by means of a movable bearing, preferably a feather key or a spline connection, arranged on the output shaft. As a result, axial tolerances but also

Heat expansions are compensated. Jamming the drive hub for Output shaft is prevented. The torque transmission of the

Output shaft on the conveyor thus has high efficiency in all operating conditions. In advantageous embodiments, a shaft sealing ring arranged between the working space and the two shaft bearings separates the two shaft bearings from the working medium in a media-tight manner. As a result, the working medium, which often has poor lubricating properties, kept away from the wear-critical shaft bearings, which in turn can be lubricated in further developments by means of a suitable lubricant. The life of the two shaft bearings is thereby increased. Furthermore, the risk of cavitation of the working medium in the shaft bearings is eliminated.

In advantageous developments, the fluid pump is positioned by means of a Einpasses to the engine. In particular, the coaxial alignment of the output shaft to the conveyor is thereby carried out very accurately, so that the

Output shaft to the conveyor is aligned. The sealing of the tooth chambers can thus take place in close tolerances. The efficiency of the motor-pump unit is thus optimized.

Advantageously, the fitting is a press connection between the

Pump housing and a motor housing of the engine running. This allows a very accurate coaxial positioning on one axis, so a concentric alignment of two parts to each other.

In advantageous embodiments, the fluid pump comprises a cover flange. The cover flange is positioned by means of centering pins to the pump housing. The fitting is made between the cover flange and a motor housing of the engine. As a result, the fluid pump is easy to assemble by the cover flange is connected to the pump housing, thus defining the working space. The centering pins indirectly the coaxial or radial

Orientation of the output shaft to the conveyor very accurately executed. The efficiency of the motor-pump unit is thus optimized. Preferably, the fit is designed as a press connection. In advantageous embodiments, the drive hub is formed on a first gear. The fluid pump is thus designed as a gear pump.

Gear pumps have a comparatively high efficiency with low production costs.

In advantageous developments, the gear pump is designed as an external gear pump or as an internal gear pump, the conveying device comprising the first gear arranged on the output shaft and a second gear meshing with the first gear. Both gears are arranged in the working space. The torque transmission from the output shaft of the motor to the first gear is thereby carried out very effectively.

The above-described fluid pumps or external gear pumps are very well suited for use in waste heat recovery systems of

Internal combustion engines. Such waste heat recovery systems often use low viscosity, poorly lubricious working media. The fluid pump according to the invention enables a fluidic separation of its two shaft bearings from the working space, so that wear and cavitation in the shaft bearings are reduced or eliminated. Therefore, the fluid pump or motor-pump unit 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 motor-pump unit according to an embodiment with the features described above.

Brief description of the drawings

Hereinafter, embodiments of the invention below

With reference to the accompanying drawings described in more detail. 1 shows a motor-pump unit of the prior art in one

Sectional view, with only the essential areas are shown. Fig. 2 shows an inventive motor-pump unit in a

Sectional view, with only the essential areas are shown.

Embodiments of the invention

1, a motor-pump unit 80 of the prior art is shown in a sectional view. The motor-pump unit 80 includes a motor 90 configured as an electric motor, and a fluid pump 100 configured as one

External gear pump, wherein the external gear pump 100 of the

Electric motor 90 is shown axially displaced.

The external gear pump 100 includes a pump housing 7, an end cap 7a and a lid flange 7b. The end cover 7a and the cover flange 7b are clamped together with the interposition of the pump housing 7 by screws, not shown. The pump housing 7, the end cover 7a and the cover flange 7b define a working space 20. In the working space 20, a first gear 9 and a second gear 19 are arranged in mesh with each other and thus constitute a conveyor 101 of the fluid pump 100. By the combing of the two gears 9, 19, the conveyor 101 conveys a working fluid from an inlet, not shown, to an outlet, not shown. Inlet and outlet are in the

Pump housing 7 and formed in the end cap 7a or in the cover flange 7b and open into the working space 20th

Both gears 9, 19 have a certain number of teeth. The first gear 9 is mounted on a drive shaft 8 and the second gear 19 on a parallel to the drive shaft 8 further shaft 18. Alternatively, depending one

Gear and one wave also be made in one piece. The drive shaft 8 of the external gear pump 100 is connected to an output shaft 2 of the electric motor 90. The two shafts 8, 18 each protrude through their associated gear 9,

19 and are firmly connected to this, for example, by one each Press Association. On both sides of the gears 9, 19, the shafts 8, 18 are mounted. The storage is carried out by two bearing glasses 6, 16, wherein the bearing glasses 6, 16 are arranged in the working space 20: a bearing glasses 6 is disposed adjacent to the end cover 7a and another bearing glasses 16 adjacent to the cover flange 7b. In both bearing glasses 6, 16 are each two bushings 17 are pressed. The bushings 17 of the other bearing glasses 16 store the two shafts 8, 18 on the drive side and the bearing bushes 17 of the bearing glasses 6 on the opposite side of the gears 9, 19. The bushings 17 thus form bearings, more precisely bearings for the two shafts 8, 18 , Alternatively, two bushings 17 can also be made in one piece with the bearing goggles 6 or with the further bearing goggles 16.

The four bushings 17 each have a radial bearing function and each form a plain bearing with their associated shaft 8, 18. Die

Axial bearing function is achieved by the two bearing goggles 6, 16: For this purpose, the bearing goggles 6 on the front side a stop surface 6a and the other bearing goggles 16 frontally another stop surface 16a. Both stop surfaces 6a, 16a cooperate with both gears 9, 19. The abutment surface 6a supports both gears 9, 19 oriented in the axial direction to the end cap 7a; the further stop surface 16a supports both gears 9, 19 oriented in the axial direction to the cover flange 7b.

Alternatively to the plain bearing, the bearing of the two shafts 8, 18 may also be designed by means of rolling bearings.

To seal the working space 20 to the environment not shown seals on the pump housing 7 are arranged. Furthermore, a shaft seal 5 is arranged at the shaft drive of the drive shaft 8 between the cover flange 7b and the drive shaft 8.

The motor designed as an electric motor 90 comprises a motor housing 25, in which the output shaft 2 is rotatably mounted. The electric motor 90 further comprises a stator 26 and a rotor 27. The rotor 27 is fixedly connected to the output shaft 2 or designed in one piece with this. The stator 26 is arranged stationarily in the motor housing 25. The output shaft 2 and thus also the rotor 27 are by means of a first shaft bearing 1 a and a second Shaft bearing 1 b stored in the motor housing 25. The two shaft bearings 1 a, 1 b are also arranged in the motor housing 25 for this purpose. The two

Shaft bearing 1 a, 1 b can be designed both as a rolling bearing and as a sliding bearing.

The two shaft bearings 1 a, 1 b are sealed by means of a further shaft seal 3 to the surroundings of the motor 90. For this purpose, the further shaft sealing ring 3 is arranged on the shaft through drive of the output shaft 2 to the motor housing 25 in the radial direction between the motor housing 25 and the output shaft 2.

The motor-pump unit 80 further includes a clutch 4. The clutch 4 is disposed between the engine 90 and the fluid pump 100 and mechanically connects the output shaft 2 to the first shaft 8 so that the drive torque generated in the motor 90 is applied to the drive shaft 8 of the fluid pump 100 is transmitted. For this purpose, the clutch 4 on each one end face of

Output shaft 2 and drive shaft 8 inserted.

For coaxial alignment of output shaft 2 to drive shaft 8, the pump housing 7 and the motor housing 25 are aligned by means of a Einpasses 1 1 to each other. The fitting 1 1 comprises a formed on the motor housing 25 guide surface 1 1 a and formed on the pump housing 7 positioning 1 1 b, both of which are cylindrically shaped and form a clearance fit or a press fit in the assembled state. By this orientation of the motor housing 25 to the pump housing 7, the two shaft bearings 1 a, 1 b of the motor housing 25 coaxial with the

Bearing bushes 17 of the drive shaft 8 aligned, and thus the output shaft 2 of the motor 90 and the drive shaft 8 of the fluid pump 100 are aligned coaxially with each other. The concentricity of the two shafts 2, 8 is thus optimized.

Nevertheless, due to dimensional and position tolerances deviations in the coaxiality between the output shaft 2 and the drive shaft. 8

2 shows a motor-pump unit 80 according to the invention in one

Sectional view, with only the essential areas are shown. The motor 90 and the fluid pump 100 in this case have a common shaft 2. The output shaft 2 of the motor 90 designed as an electric motor is also the drive shaft of the fluid pump 100 designed as an external gear pump.

This eliminates the first shaft 8 and the first shaft 8 superimposed

Bushings 17 of the fluid pump 100 of the prior art according to Fig.1. Furthermore, the coupling 4 is omitted for connecting the two shafts 2, 8.

Thus, the motor-pump unit 80 includes the fluid pump 100 and the motor 90. The motor 90 has the output shaft 2, which by the first

Shaft bearing 1 a and the second shaft bearing 1 b is mounted in the motor housing 25. The output shaft 2 projects out of the motor housing 25 and enters the pump housing 7. In the working space 20 of the fluid pump 100 is a

Drive hub 102 of the conveyor 101 mounted on the output shaft 2. Since in the embodiment of FIG. 2 the fluid pump 100 is designed as an external gear pump, the drive hub 102 is formed on the first gear 9.

The second gear 19 is mounted on a arranged on the pump housing 7 housing pin 7c. For this purpose, the second gear 19 is cup-shaped. Alternatively, however, other bearings of the second gear 19 would be possible, for example by means of bearing bushes, as described in the prior art.

The fluid pump 100 may be embodied in alternative embodiments of the external gear pump, for example, as an internal gear pump or vane pump. In both cases, the drive shaft of the fluid pump 100 corresponds to the output shaft 2 of the motor 90. In the internal gear pump, the output shaft 2 is preferably connected to the inner gear, so with the pinion. In the vane pump, preferably, the rotor is fixedly connected to the output shaft 2, while preferably the blades do not rotate.

In advantageous embodiments, the drive hub 102 and the first gear 9 is arranged axially movable as a movable bearing 13 on the output shaft 2, so that high torques can be transmitted and axial tolerances or thermal expansion can be compensated. The floating bearing 13 of the output shaft 2 to the first gear 9 can be done for example by means of one or more feather keys or by means of a splined connection. As a result, the axial mobility of the output shaft 2 is decoupled from the fluid pump 100. This applies to all Embodiments of the fluid pump 100, in particular for external gear pumps, for internal gear pumps and for vane pumps.

To improve the sealing of the working space 20 and the drive through the output shaft 2 through the cover flange 7b, the output shaft is the second

advantageously positioned exactly to the pump housing 7. Thereby, the sealing of the tooth chambers to the pump housing 7 is made in close tolerances, so that the leakage is minimized, and the volumetric efficiency of the fluid pump 100 is increased. The exact positioning is preferably carried out by the fitting 1 1 between the motor housing 25 and pump housing 7 or by centering pins 10, which align the cover flange 7b to the pump housing 7. Preferably, however, both the Einpass 1 1 and the centering pins 10 are used, both fits can be performed with or without interference fit.

In advantageous embodiments, the motor-pump unit 80 uses only a single shaft seal 5 for sealing the working space 20 to the shaft bearings 1 a, 1 b. This is arranged in the embodiment of Figure 2 in the radial direction between the output shaft 2 and the motor housing 25. The shaft seal 5 may alternatively but also to the pump housing 7 and zum

Cover flange 7b to be arranged.

On the opposite side of the motor 90, the gears 9, 19 cooperate with a sealing washer 12, which is arranged in the pump housing 7. The sealing washer 12 can be firmly connected to the pump housing 7, or be stored floating in this. In the embodiment of Figure 2, the sealing washer 12 is disposed between the end faces of the gears 9, 19 and the end cover 7b. The sealing disc 12 serves the axial sealing of the tooth chambers and is accordingly preferably made of a tribologically favorable material.

The illustrated fluid pump 100 is very well suited for low-lubricating, low-viscosity working media, as they are for example in

Waste heat recovery systems are used for internal combustion engines. In particularly advantageous embodiments, the engine according to the invention

Pump unit 80 therefore in a waste heat recovery system a Internal combustion engine arranged, wherein the fluid pump 100 does not necessarily have to be designed as external gear pump. Of the

Internal combustion engine is supplied 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.

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 vaporized 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.

The feed fluid pump of the waste heat recovery system is a fluid pump 100 of a motor-pump unit 80 according to one of the above

Versions. These are especially good for one

Waste heat recovery system, as it also for bad lubricating

Working media with very low viscosities are suitable. By separating the two shaft bearings 1a, 1b from the working medium of the fluid pump 100, on the one hand the risk of cavitation in the shaft bearings 1a, 1b is minimized. On the other hand, significantly better lubricants than the working medium of the fluid pump 100 can be used for lubricating the shaft bearings 1a, 1b. The wear in the shaft bearings la, lb is thereby significantly reduced. The fluid pump 100 is thus also suitable for operating temperatures which are close to the evaporation temperature of the working medium and are therefore particularly suitable for use in waste heat recovery systems.

Claims

claims

A motor-pump unit (80) having a motor (90) and a fluid pump

(100), wherein the fluid pump (100) comprises a pump housing (7), wherein in the pump housing (7) an inlet and an outlet are formed, wherein the pump housing (7) defines a working space (20), wherein in the working space ( 20) a working medium by means of a conveyor

(101) is conveyable from the inlet to the outlet, wherein the motor (90) has a drive output shaft (2), wherein the output shaft (2) by means of a first shaft bearing (la) and by means of a second shaft bearing (lb) in the Motor (90) is mounted, wherein the

Conveyor (101) has a drive hub (102),

characterized in that

the drive hub (102) on the output shaft (2) is arranged.

2. Motor-pump unit (80) according to claim 1

characterized in that

the drive hub (102) by means of a movable bearing (13), preferably a keyway or a splined connection, on the output shaft (2) is arranged.

3. motor-pump unit (80) according to claim 1 or 2

characterized in that

a between the working space (20) and the two shaft bearings (la, lb) arranged shaft seal (5), the two shaft bearings (la, lb) media-dense separates from the working fluid.

4. Motor-pump unit (80) according to one of claims 1 to 3

characterized in that

the fluid pump (100) is positioned by means of a fitting (11) to the motor (90).

5. motor-pump unit (80) according to claim 4

characterized in that the fitting (11) is designed as a press connection between the pump housing (7) and a motor housing (25) of the motor (90).

Motor-pump unit (80) according to claim 4

characterized in that

the fluid pump (100) comprises a cover flange (7b), wherein the

Cover flange (7b) by means of centering pins (10) to the pump housing (7) is positioned, wherein the fitting (11) between the cover flange (7b) and a motor housing (25) of the motor (90) is carried out, preferably as a press connection.

Motor-pump unit (80) according to one of claims 1 to 6

characterized in that

the drive hub (102) is formed on a first gear (9).

Motor-pump unit (80) according to claim 7

characterized in that

the fluid pump (100) as an external gear pump or as

Internal gear pump is executed, wherein the conveyor (101) on the output shaft (2) arranged first gear (9) and with the first gear (9) meshing second gear (19), wherein the two gears (9, 19) in the working space (20) are arranged.

Waste heat recovery system comprising a working medium carrying 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 motor-pump unit (80) according to one of claims 1 to 8.