DE102010064061A1 - Turbo compressor for fuel cell drive of internal combustion engine of hybrid drive for motor vehicle, has drive unit and two compressor wheels driven by drive unit - Google Patents

Abstract

The turbo compressor has a drive unit and two compressor wheels driven by the drive unit, where the compressor wheels are respectively arranged in two compressor housings (12,22) in a rotatable manner. An intermediate cooler is arranged with a gas line, with which the flowing gas is compressed from the former compressor wheel and is cooled from another compressor wheel. Independent claims are also included for the following: (1) a method for compressing gas, particularly air by a turbo compressor; (2) a fuel cell drive with a fuel cell; and (3) an internal combustion engine formed as a component part of a hybrid drive.

Description

The present invention relates to a turbocompressor having two compressor wheels, which are arranged axisymmetric and between which a gas line is arranged to allow a gas flow.

Moreover, the present invention relates to a method for compressing gas, in particular of air, by means of the turbocompressor according to the invention. In addition, the present invention relates to a fuel cell drive and an internal combustion engine and a motor vehicle.

Gas compressors are used to compress gas, which is supplied with the admixture of fuel to an internal combustion engine. As a result, the efficiency of the internal combustion engine can be increased. Since there is a demand for low consumption rates of the engine, especially in internal combustion engines in motor vehicles, a compressor is to be carried in these motor vehicles.

Another requirement that is increasingly being placed on motor vehicles is weight minimization and energy efficiency. Since most compressors are operated by an electric motor drive, there is thus an essential requirement on the compressor that it can be operated with a low electrical power consumption, in particular if it is used to operate a combustion unit, which complements the electric motor drive in a hybrid vehicle supported. In such vehicles, a compressor is therefore to be designed with low weight, preferably also low volume and with low electrical power consumption.

Conventional compressors can usually only meet one or a few of the above requirements.

In the DE 694 25 891 T2 For example, a compressor is described which is arranged to balance an axial load on the bearings so that wear of the bearings is reduced.

Furthermore, compressors are known which exploit thermal engineering processes.

In the DE 200 11 217 U1 a turbocompressor is described, the drive unit is cooled with the fluid, which is conveyed by the turbo compressor. This means that in this turbocompressor heat is transferred from the engine to the pumped medium, so that it is heated.

The WO 2002/099286 A1 describes a compressor unit with cooling for engine and bearing to avoid premature wear of the engine and the bearings at high speeds. The gas to be compressed is not subjected to heat treatment.

The EP 0355796 B1 describes a so-called centrifugal pump, in which a coolant flow is generated. However, the coolant flow has no influence on the gas to be compressed.

The DE 198 14 485 A1 discloses a turbo fan with two impellers driven by a motor. Between the two wheels, an intercooler for cooling the compressed medium is arranged.

The invention has for its object to provide a compressor and a method for compressing gas available, which allow energy-efficient compression of gas in a simple, weight-saving, reliable and cost-effective design.

This object is achieved by the turbocompressor according to claim 1 and the method for compressing gas according to claim 12. Advantageous embodiments of the turbocompressor are specified in the subclaims 2-11. An advantageous embodiment of the method for compressing gas is specified in the dependent claim 13. In addition, a fuel cell drive according to claim 14, an internal combustion engine according to claim 15 and a motor vehicle according to claim 16 are proposed, which has a fuel cell drive or an internal combustion engine.

According to the invention, a turbocompressor is provided which comprises at least one drive unit and at least one first and one second driven by the drive unit, rotatably disposed in each of a first and a second compressor housing compressor wheel, wherein the first and the second compressor substantially axially symmetrical aligned with each other a common shaft are arranged and the first compressor housing with at least one gas line fluidly connected to the second compressor housing for conducting gas compressed from the first compressor to the second compressor wheel for the purpose of recompression.

According to the invention, at least one intercooler, with which the gas compressed by the first compressor wheel and flowing to the second compressor wheel can be cooled, is arranged with the gas line in a heat-coupled manner.

It is a radial compressor. The drive unit is preferably an electric motor whose rotor forms the shaft. Optionally, the drive torque of several drive units can be transmitted to the shaft.

The compressor wheels essentially have a conical shell shape, that is, when designed as a turbine wheel, the compressor wheel has a turbine blade, which on the shaft or on its side facing the shaft has a greater width than at its radial end.

The compressor housing may be an integral part of an entire housing or it may be made individually.

The compressor wheels are arranged on a common shaft, wherein preferably at one end of the shaft, a compressor wheel is arranged. The entry of a torque in the shaft for the purpose of driving takes place between the compressor wheels.

The compressor wheels are preferably arranged axisymmetric, that is, the axis of symmetry is perpendicular to the shaft longitudinal axis. The sides with the smaller diameters of the conical shell shape of the two compressor wheels point in opposite directions. Preferably, they point away from each other.

As a result, the axial forces introduced into the shaft by both compressor wheels are oppositely oriented so that at least partial cancellation of the axial forces introduced into the shaft occurs.

The gas line can be a channel integrated in the housing and thus a gas reservoir or an extra line which serves to direct the gas which has been compressed by the first compressor wheel to the second compressor wheel for the purpose of recompression.

The gas conduit is arranged and arranged such that heat from the gas compressed by the first compressor wheel in the gas conduit is transferable to the intercooler so as to reduce the temperature of the compressed gas prior to entering the second compressor stage and thus also reduce the volume of the gas ,

This ensures that the second compressor stage or the second compressor wheel per gas quantity must apply less power and thus a higher efficiency can be achieved.

The advantage of combining the axisymmetric arrangement of the compressor wheels and the intermediate cooling is that at least partially the axial forces are canceled by the axisymmetric arrangement. As a result, smaller bearings for supporting the shaft are used, since they do not have to absorb large axial forces. Thus, a correspondingly smaller dimensioning of the shaft or the shaft journal for receiving the bearing is possible. This in turn allows very high speeds. But very high speeds can only be realized if a high drive power is provided or the removable torque may be relatively low.

Due to the intermediate cooling, the overall efficiency can be increased, thus no longer a very large torque is required for compression. This means that although a high speed would be generated without the intermediate cooling, however, a high power would have to be made available in order to provide the torque required for the second compressor stage. Only by combining the axisymmetric arrangement with the intermediate cooling can be realized by both compressor stages with low drive power, for example, electric drive power, a high speed and a sufficient compression ratio.

In a preferred embodiment, the turbocompressor with intercooler comprises at least one cooling device for cooling the drive unit, wherein the intercooler is thermally coupled to the cooling device.

The cooling device can also be called engine cooling and is preferably designed as an integral part. It is thus possible heat transfer between the intercooler and the cooling device.

It can be provided in particular that the intercooler for cooling bearings for the storage of moving parts, in particular the shaft, the turbo compressor is configured, wherein the intercooler is thermally coupled with the gas line such that heat of the gas in the gas line in the cooling liquid in the intercooler and optionally transferable in the cooling device.

Thus, the effect is caused that cooling liquid, which is guided for cooling the shaft bearings in the vicinity, is also used to dissipate heat from the compressed in the first stage gas.

In a preferred embodiment it is provided that the shaft is a component of a rotor of an electric motor drive unit. In an alternative embodiment, the shaft may also be an output shaft of a turbine of a turbocharger.

It is further provided that on the shaft at least one magnet is arranged and thus the shaft forms a rotor of an electric motor, wherein the magnet is secured in the direction of the longitudinal axis of the shaft on both sides by a respective bandage.

That is, the rotor comprises magnets pressed against the shaft, which are secured against displacement by bandages. These bandages are shrunk onto the shaft both in front of and behind the magnets in the axial direction. In an alternative embodiment it is provided that the magnets are glued to the shaft. This embodiment is advantageously formed in that on the shaft - the magnet and the bandages at least partially overlapping - a jacket element is arranged.

The shell element is shrunk as a "reinforcement", which can optionally be welded to the annular bandages. This leads to a considerable increase in the stiffness of the composite shaft, which in turn is crucial for the shaft design. A welding or brazing of the bandages leads arithmetically to a "total body" by the cohesive connection. Advantageously, the reinforcement is made of stainless steel.

It may further be provided that the shaft for receiving bearings at both ends in each case has a shaft journal, wherein at least in one of the shaft journal a longitudinal bore is introduced, in which a temperature sensor is positioned or positioned.

That is, in the meantime there are holes that are used for temperature measurement of the bearing inner rings during operation. For this purpose, temperature sensors can be introduced or it is carried out a non-contact measurement in the bore.

In a particular preferred embodiment, it is provided that the first compressor wheel has a diameter which is at least 1/10 larger than the diameter of the second compressor wheel.

By pre-compression of the gas in the first compressor stage, the second compressor stage must bring higher power. With the same dimensioning of the compressor wheels different axial forces would act on the bearings and the shaft, so that no compensation of the axial forces would occur and the bearing would have to absorb axial forces. To avoid this, the second compressor wheel is dimensioned slightly smaller than the first compressor wheel.

Furthermore, it is preferably provided that the cooling device has at least one helical flow channel.

That is, for example, the water cooling around an electric motor takes place in the form of a screw thread. The cooling device is preferably a liquid cooling system.

In this case, the compressor may be configured such that it has at least two bearings for supporting the shaft and the cooling device is configured such that with her in the camps generated heat can be derived.

In addition, this allows the rear walls of the bearing housing on the compressor wheels water cool, causing an improvement in efficiency.

Preferably, the intercooler is thermally coupled to the cooling device.

The bushings for receiving the bearings are advantageously cast in the housing and can be designed to achieve a high accuracy of steel. In a preferred embodiment, it is also provided that the liquid cooling for cooling the bearings associated with each bearing has at least one annular channel which has a distance from the respective bearing of less than 20 mm. This annular channel may be part of the helical flow channel.

The annular channel extends to at least 20 mm, preferably less than 10 mm, in particular less than 5 mm and in a particularly preferred embodiment less than 2-4 mm zoom to the bearing bush.

In a dense steel bushing or ceramic bushing of the bearing, the cooling liquid can also be performed directly to the bush of the bearing when the cooling channel in the housing is open on the storage side.

According to the invention, the shaft is mounted with a rolling bearing designed as a floating bearing and a rolling bearing configured as a fixed bearing, wherein the floating bearing is clamped in the axial direction by means of at least one plate spring.

Advantageously, the rolling bearings are arranged in an O arrangement. The plate spring is supported on a retaining ring which is seated in a bearing bush, so that the force generated by the plate spring is directed against the outer ring of the rolling bearing. The floating bearing is biased axially by the plate spring. That is, the inner ring of the bearing is stuck on the shaft and the spring washer of the diaphragm spring presses on the outer ring. As a result, the high Hertzian pressure is reached, due to which a high critical speed can be realized. The preload force is up to 250 N, in order to guide the rolling elements optimally in the Kalottenbahnen.

The direction of the axial bias corresponds to the direction of the shaft longitudinal axis.

The plate spring of the turbocompressor is preferably set up in such a way that it applies substantially the same force to the outer ring of the movable bearing in the installed state between the bearing bush and the bearing outer ring, independently of the thermal expansion of the shaft. That is, the plate spring is arranged biased so that when heat change caused linear expansion of the shaft with a certain way the spring characteristic has substantially no slope, so that the spring force remains the same regardless of the compression travel.

The spring characteristic thus has a horizontal asymptote at the operating point or in the operating section. This means that due to thermal expansion, the axial bias does not change during operation and thus the angle of the ball adjustment remains unchanged, which is crucial for the life of the storage. The axial preload of the bearing can be performed up to the load limit of the material of the bearing inner rings. The higher the preload, the stiffer the storage, which in turn increases the critical bending speed.

By this measure, a very stiff shaft bearing is realized, that is, there is a very high Hertzian pressure.

In a preferred or alternative embodiment, it is provided that the shaft is mounted with roller bearings, which are designed as sealed hybrid bearings.

A hybrid bearing is a ball bearing with conventional bearing rings made of bearing steel and balls made of a high-strength ceramic, in particular a Siliziumnitridkeramik.

The advantage of ceramic balls is the interruption of the magnetic flux. In addition, when using the turbocompressor for fuel cell air supply occur no contamination as with a conventional oil lubrication or oil mist lubrication.

Advantageously, the rolling bearings are lubricated for life grease. Due to the encapsulation of the rolling bearings no leakage of lubricant and consequently no contamination of the compressed gas is to be feared.

In a further advantageous embodiment, it is provided that each of the compressor housing forms a compression space and the shaft is arranged in a rotor space which is delimited by the compression spaces, wherein at least one of the compression chambers with the rotor space by means of a bypass for realizing a gas flow from this compression space is connected in the rotor space.

The bypass thus represents a parallel wiring harness to a gas line connecting the compressor housing.

The bypass can be designed in the form of one or more holes between the compression space and the rotor space. It ensures that any occurring pressures are not passed through the bearings, otherwise it could lead to a rinsing out of the bearing grease and thus to the failure of the bearings in the long term. This means that without the bore a steady pressure would be exerted on the bearings, which could lead to a rinsing of the bearings and contamination of the compressed gas with lubricant particles during prolonged operation. Consequently, the formation of oil mist can be prevented by the drilling.

The rolling bearings are preferably water-cooled or water-cooled.

To seal the compression space, it is provided that the compressor wheels and the compressor housings assigned to them form at least one labyrinth seal by means of complementary shaped elements. In this case, the compressor housing in the region of the labyrinth seal may be part of a motor housing for receiving and supporting the shaft serving as a rotor. The labyrinth seal is thus arranged on the back of a compressor wheel, that is, on the side of its larger circumference.

Advantageously, the turbo-compressor is configured such that a nominal rotational speed of the shaft of at least 60,000 can be realized min ^-1, wherein the compressor has a critical rotational speed that is greater than the rated speed.

The turbocompressor is particularly adapted for rotational speeds in excess of 80,000 min ^-1 and advantageously about 100,000 min ^-1. In a particular embodiment, the turbo-compressor for a speed of up to 125,000 is designed min ^-1. The turbocompressor can therefore be operated subcritically. This has the distinct advantage of not having to drive through critical speeds is. The compressor can use its entire working area to compress the air.

In a preferred embodiment, the shaft has a ratio of total length of the shaft Lw to the maximum diameter Dw of the shaft of Lw / Dw = 6 to 8. This means that a very short and compact shaft is used so that the critical speed is very high.

Preferably, the ratio of the total length of the shaft Lw to the maximum diameter Dw of the shaft is Lw / Dw = 7.3, the length of the bilateral shaft journals being included in the length Lw.

In addition, it can be provided that at least one of the shaft journals has a ratio of overall length of the shaft journal Lz to the maximum diameter Dz of the shaft journal of Lz / Dz = 3 to 5.

Preferably, the ratio Lz / Dz = 4.3. The preferred length of the shaft is 175 mm. The preferred length of a shaft journal is 39 mm. The preferred maximum diameter of the shaft is 24 mm. The preferred average diameter of the shaft journals is 9 mm.

For efficient gas cooling, provision can furthermore be made for a gas reservoir to be arranged in a housing of the turbocompressor in the immediate vicinity of a cavity which is at least partially filled or filled with cooling liquid.

The gas reservoir can be formed by the gas line or can be fluidically connected to it and is preferably arranged so close to the cavity at least partially filled or filled with cooling liquid, that at least 50% of the heat of the gas is transferable into the cooling liquid.

Advantageously, a wall of the gas line or of the gas reservoir is designed as a wall of the coolant line.

In addition, it is preferably provided that the cooling device has at least one first collector for temporarily storing cooling liquid to be supplied from the bearings and the gas reservoir and at least one second collector for collecting the cooling liquid coming from the bearings and the gas reservoir. This means that the engine cooling and cooling of the two bearing points takes place via a collector integrated in the motor housing, from which all three circuits (motor cooling, cooling of the first bearing and cooling of the second bearing) are fed. After flowing through these three circuits, the cooling water is collected in an integrated collector and then transferred to the cooling device of the vehicle.

The invention also relates to a method for compressing gas, in particular air, by means of a turbocompressor, which comprises at least one drive unit and at least a first and a second drivable by the drive unit drivable, in each case a first and a second compressor housing rotatably arranged compressor wheel, wherein the the first and the second compressor wheel are arranged substantially axially symmetrical aligned with each other on a common shaft and the first compressor housing with at least one gas line fluidly connected to the second compressor housing for directing compressed gas from the first compressor to the second compressor wheel for re-compression. According to the invention, the gas compressed by the first compressor wheel in a first compression stage is fed through the gas conduit to the second compressor wheel for compression in a second compression stage, the gas being cooled between the first compression stage and the second compression stage by means of at least one intercooler. That is, the gas compressed by the first compressor stage is cooled prior to compression in the second compressor stage. Thus, the method can be carried out in particular with a turbocompressor according to the invention.

The cooling liquid in the intercooler is preferably water or a mixture of water and a coolant.

In order to avoid passing through a critical speed range, it is provided that the turbocompressor is operated at a rotational speed of the shaft which is below the critical rotational speed of the turbocompressor. The turbocompressor for performing the method is arranged such that a nominal rotational speed of the shaft of at least 60,000 can be realized min ^-1, wherein the compressor has a critical rotational speed that is greater than the rated speed.

It is preferably provided that the overall compression ratio realized by the two compression stages is at least 1 bar. Advantageously, compression ratio is above 2 bar and in a particular embodiment 2.6 bar.

It is also provided to prevent overheating that the temperature of the shaft bearings is measured during operation of the turbocompressor. The temperature determination can be carried out in particular by infrared measurement. The speed of the compressor can be controlled as a function of the temperatures measured in the bearings.

The process can be carried out such that the compression ratio is at least 1.5 bar with a gas quantity of at least 50 g / s. Advantageously, the turbocompressor is set up such that a compression ratio of up to 2.6 bar with an air quantity of 80 g / s can be achieved with it during the compression of air, wherein the feasibility of other compression ratios should not be excluded.

The compression ratio is preferably 2.6 bar with a gas quantity of 80 g / s. In particular, the process for compressing a gas or a gas mixture is carried out by means of a two-stage compression, wherein the gas at the entrance to the first compression stage, a temperature of 293 K and in the first compression stage, a temperature of 383 K, by the liquid cooling by at least 20 K. is cooled, the second compression stage is supplied and is heated to 389 K in the second compression stage.

When the compressor is operated in a hybrid vehicle, a renewed cooling in a cooler then takes place to a desired operating temperature. The cooling in the intermediate cooling as well as in the final cooling in the hybrid should be at least 20 K, in particular more than 30 K, preferably at least 40 K and preferably 50 K.

When used in a fuel cell vehicle, no further cooling takes place, since warm air is used in the fuel cell vehicle.

The invention additionally provides a fuel cell drive and an internal combustion engine, wherein the fuel cell drive has at least one fuel cell for generating electrical energy and a compressor according to the invention for supplying compressed air to at least one fuel cell.

The compressor according to the invention can be used in particular for the fuel cell air supply.

The internal combustion engine is in particular an internal combustion engine as part of a hybrid drive of a motor vehicle and, in addition to an internal combustion engine, comprises a compressor according to the invention for supplying compressed air to the internal combustion engine.

The invention is supplemented by a motor vehicle which has a fuel cell drive according to the invention or an internal combustion engine according to the invention.

The invention is explained below with reference to the example of a two-stage compressor shown in the accompanying figures. Show it:

1 a compressor according to the invention in perspective view,

2 a sectional view of the compressor according to the invention,

3 a further sectional view of the compressor according to the invention along a different cutting path than in 2 shown,

4 a storage representing the cutout 3 .

5 another storage representing the cutout 3 .

6 a schematic representation of the intermediate cooling,

7 a further sectional view of the compressor according to the invention,

8th a single representation of the rotor shaft and

9.1 to 9.4 Process stages in the manufacture of the rotor shaft.

The two-stage compressor is equipped with essentially axially symmetrical compressor wheels, electrically driven and radial design. Preferably, the compressor for supplying fuel cells with compressed air is to be used, but its application in internal combustion engines, especially in hybrid vehicles, for the preparation of the fuel-air mixture is also possible. The desired compression ratio can be up to 2.6 bar with an air volume of 80 g / s.

How out 1 is apparent, is on the motor housing 1 a housing cover 2 as well as left and right of the motor housing 1 a first compressor stage 10 and a second compressor stage 20 arranged. Each of the compressor stages 10 . 20 includes a first compressor housing 12 respectively 22 in which a in 1 not shown first compressor wheel 11 or second compressor wheel 21 is arranged rotated or rotatable. Each of the compressor housing 12 . 22 includes a first intake manifold 13 respectively 23 which is substantially axial to the motor housing 1 is aligned, and a first outlet 14 respectively 24 , which is substantially tangential to the respective compressor housing 12 . 22 connected. In the first compressor stage 10 Air is sucked in and out compressed and to the second compressor stage 20 transported, as it in particular 6 is apparent. The transport line of the gas from the first compressor stage 10 to the second compressor stage 20 is in 1 not shown.

It is thus possible upon actuation of the engine, the compression of air simultaneously in two compressor stages 10 . 20 realize, so that the required construction volume for the compressor according to the invention is very low.

2 shows a cross section through the compressor according to the invention. Visible is the centrally arranged motor housing 1 and the housing cover arranged on the left 2 , To this housing cover 2 closes the first compressor housing 12 at. In this compressor housing 12 is the first compressor wheel 11 , The first compressor wheel 11 sits on the shaft journal 31 a continuous rotor shaft 30 , This rotor shaft 30 is in relation to the first compressor stage 10 with a rolling bearing 50 stored, which in a bearing bush 54 is arranged, with this bearing bush 54 in the housing cover 2 supported. Essentially arranged axially symmetrically on the right side of the motor housing 1 the second compressor housing 22 provided, which in turn is the second compressor wheel 21 which is also on a shaft journal 31 the rotor shaft 30 is arranged. Also this second compressor wheel 21 is by means of a rolling bearing 51 stored. This rolling bearing 50 on the second compressor stage 20 is in a bearing bush 54 taken, which are in the motor housing 1 supported.

The rolling bearing 50 the first compressor stage 10 is arranged as a fixed bearing and the rolling bearing 50 the second compressor stage 20 as a floating warehouse. For axial adjustment of the rolling bearing 50 the second compressor stage 20 is a plate spring 60 arranged, whose force is on the rolling bearing 50 is directed, and which is about a circlip 62 at the bearing bush 54 axially supported.

It can be seen that the rotor shaft 30 for receiving and for driving both compressor wheels 11 . 21 serves. It is constructed as a rotor of an electric motor, wherein the stator of the electric motor through the motor housing 1 or is realized by therein windings and / or magnets.

The rotor shaft 30 is built relatively compact, as it especially made 8th is apparent. That is, their ratio of maximum length to maximum diameter is only 6 to 8, and preferably 7.3. The length is defined including the shaft journal lengths.

A respective shaft journal has a ratio of length Lz to the maximum diameter Dz of the shaft journal of Lz / Dz = 3 to 5, preferably 4.3.

Preferably, the length of the rotor shaft is more than 160 mm to 195 mm, preferably 175 mm. The preferred length of a shaft journal is between 30 mm and 50 mm, preferably 39 mm. The preferred maximum diameter of the shaft is between 20 mm and 30 mm, preferably 24 mm. A preferred shaft journal diameter is between 7 mm and 11 mm, preferably 9 mm.

On the rotor shaft 30 are magnets 33 fastened, which have a substantially hollow cylindrical shape. These magnets 33 can on the rotor shaft 30 be pressed. The side or the magnets are 33 by means of bandages 34 secured against displacement. These bandages 34 are advantageously made of a ferrous material and are shrunk onto the shaft. The magnet 33 as well as the bandages 34 At least partially overlapping again is a so-called reinforcement 35 Shrunk, if necessary, with the bandages 34 , if mechanically required, can be welded. This leads to a considerable increase in the rigidity of the entire composite shaft, so that in total the rotor shaft 30 or the entire wave composite with smaller diameters and thus lower moments of inertia is executable. The reinforcement 35 can be made of stainless steel.

In an alternative embodiment it is provided that the magnet 33 or the magnets 33 on the rotor shaft 30 are glued.

Also in 8th It is shown that in the shaft at both axial bores 32 arranged to receive temperature sensors 40 serve. The holes 32 extend so deep axially into the rotor shaft 30 in that they have substantially the same distance to the shaft journal ends as the shoulders for receiving the roller bearings 50 , As a result, temperature sensors can 40 so deep into the holes 32 be introduced that by means of the temperature sensors 40 essentially the temperature of the shaft journal 31 in this place and thus also the temperature of the rolling bearings 40 and optionally the bearing bushes 54 can be determined during operation of the compressor. The temperature can be determined in particular by infrared measurement.

The rolling bearings 50 for supporting the rotor shaft 30 are on each a paragraph on the shaft journal 31 arranged, which the respective compressor stages 10 . 20 are assigned as it is in the 1 to 5 and 7 is shown. For storage the rotor shaft 30 only two bearings, as shown in the figures mentioned, provided. The bearings are called rolling bearings 50 executed, preferably ball bearings are applied. In particular, an O-arrangement of the ball bearings is advantageous for the formation of the compressor according to the invention, as with this O-arrangement of the compressor wheels 11 . 21 registered forces and the axial load by the particular in 5 apparent plate spring 60 can be well received.

The biasing force caused by the diaphragm spring is up to 250 N, around the rolling elements 51 or balls optimally lead in their Kalottenbahnen. This will cause the entire bearing of the rotor shaft 30 very stiff and a very high Hertzian pressure is achieved. The rolling bearings 50 are advantageously grease lubricated for life and thus form so-called sealed hybrid bearings. The lifetime grease lubrication is particularly necessary when using the compressor according to the invention for fuel cell air supply, since no contamination of the fuel cell with lubricant particles is allowed. An oil lubrication or oil mist lubrication, which is usually used to realize very high speeds, is thus not possible when used for fuel cell air supply. However, if the use of the compressor according to the invention on an internal combustion engine, such as in a hybrid motor vehicle, provided, the storage can also be realized with oil or oil mist lubrication.

The shaft bearing of the compressor according to the invention is designed such that the compressor can achieve a speed of 60,000 min ^-1, in particular 80,000 min ^-1 and in a particularly advantageous embodiment, more than 100,000 mm ^-1. Best results in terms of energy requirements and performance are achievable at a speed of 125,000 mm ^-1 . Here are the rotor shaft 30 and the entire compressor is designed so that it is operated subcritical even at a speed of 125,000 mm ^-1 . This means that only a speed above 125,000 mm ^{-1 represents} the critical speed at which it comes to a harmful resonance behavior. The compressor according to the invention thus has the advantage that no driving through of critical speeds to reach the operating speeds is necessary. The compressor can thus use its entire working area for the compression of air. The high speeds are particularly due to the compactness of the shaft and the compact design of the shaft journal 31 allows.

Advantageously, in each case at least a part of the rolling bearing 50 namely, the rolling element 51 and / or the bearing inner ring 52 and / or the bearing outer ring 53 Made of ceramic, a magnetic flux, starting from the rotor 30 , to interrupt. When executing the rolling bearing 50 as a ball bearing is advantageously designed the ball of ceramic. The bearing bushes 54 for receiving the rolling bearings 50 are in the motor housing 1 or in the housing cover 2 Cast in and made of steel, in order to realize a high accuracy of fit.

Preferably, both are rolling bearings 50 water-cooled. This is achieved by tightly positioning strands of engine cooling that represents the cooling device 90 near the bearing outer rings 53 the rolling bearing 50 realized, so that in the rolling bearings 50 generated heat can be delivered to the cooling water, resulting in an improvement in the overall efficiency of the compressor, see in particular 5 and 7 ,

In an alternative embodiment, the rolling bearings 50 be cooled by means of air, wherein a part of the air flow of the compressed air is branched off and passed around the bearings under heat absorption and then fed back to the compression process. It is important that the air flow is not through the bearings 50 between bearing inner ring 52 and bearing outer ring 53 may be directed, but only to the rolling bearings 50 around to realize a so-called rinsing of the bearings instead of a rinse. If sufficient space is available, the air cooling can be combined with the water cooling in the compressor.

As already mentioned, the second compressor wheel 21 the second compressor stage 20 essentially axisymmetric to the first compressor wheel 11 the first compressor stage 10 arranged as it is from the 2 . 3 . 6 and 7 is apparent. This means that both turbine wheels or compressor wheels 11 . 21 are arranged in opposite directions. During operation of the compressor, this construction essentially leads to a lifting of the compressor wheels 11 . 21 caused axial forces. This has the advantage that the entire rotor shaft 30 Consequently, it is less dimensioned and / or higher speeds can be achieved.

In a preferred embodiment it is provided that the first compressor wheel 11 the first compressor stage 10 a slightly larger diameter to the compression of air in the first stage compressor 10 to perform more efficiently. Because of that from the first compressor stage 10 compressed air of the second compressor stage 20 is supplied and these also compressed the already compressed air again, thus exist in both compressor stages 10 . 20 different pressure conditions, so that their effect in combination with the different diameters of the compressor wheels 11 . 21 As a result, the said axial forces almost or completely compensate.

The motor housing 1 is preferably made of aluminum, in which the bushings 54 are cast in steel. The motor housing 1 indicates at its the second compressor stage 20 facing side mold elements, which together with complementary executed form elements on the second compressor wheel 21 a labyrinth seal 70 train, as in particular in the 4 and 5 is apparent. This labyrinth seal 70 prevents a flow of compressed air from the compression space 81 to the rolling bearings 50 , An identical or similar labyrinth seal 70 is also between the first compressor wheel 11 as well as the housing cover 2 arranged.

The housing cover 2 have a substantially spiral shape, so that of the respective compressor stages 10 . 20 sucked compressed air is accelerated on a spiral path.

For preloading the bearings 50 is, as already mentioned and in 5 shown on the rolling bearing 50 the second compressor stage 20 a plate spring 60 arranged. This plate spring 60 is set to have a substantially horizontal asymptote when operating the compressor. This has the advantage that due to operational thermal expansion of the rotor shaft 30 the axial bias is not changed and thus the angle of the ball position remains unchanged in O-arrangement, which is particularly advantageous for the life of the storage. The axial preload of the storage can up to a load limit of the materials of the loaded components, in particular the bearing inner rings 52 , be performed. The higher the bias is realized, the stiffer the storage and the higher the critical speed and consequently the realizable operating speed without having to go through a critical area. The bearing inner ring 52 is firmly on a stock sales 36 arranged. The spring ring 61 the plate spring 60 presses against the bearing outer ring 53 , whereby the high Hertzian pressure is reached, due to which sets a critical behavior only at such high speeds that the compressor according to the invention can also be operated at a speed of 100,000 min ^-1 up to 125,000 mm ^-1 . The plate spring 60 itself relies on a circlip 62 off, which is radial in the bearing bush 54 is included. The plate spring 60 Can through one or more spring washers 61 be educated.

That of the first compressor stage 10 associated rolling bearings 50 is how in 4 shown, designed as a fixed bearing.

In particular, in the application of the compressor for supplying air to fuel cells, in which any formation of oil mist is to be prevented, the compressor should be designed such that a flow channel in the form of a bypass 80 who from the 2 . 3 and 7 is apparent, is formed. This bypass 80 allows airflow from the compressor room 81 in the rotor space 82 bypassing the rolling bearing 50 , Without the arrangement of this bypass 80 could be an air pressure increase in the compressor room 81 to an impermissible increase in the pressure on the bearings 50 to lead. This pressure exerted by compressed air could cause rolling bearings after a certain period of operation 50 flush out and the from the compressor stages 10 . 20 Contaminate generated airflow with oil. This would in addition to an impermissible load on the compressed air with lubricating oil shares also to a reduction of the lubricants in the rolling bearings 50 and thus to an extraordinary reduction in the life of the bearings 50 to lead.

The whole, by rotor shaft 30 and motor housing 1 or arranged therein windings and / or magnets realized electric motor is by means of a motor cooling 90 cooled. The engine cooling 90 is best in 3 seen. It includes one or more screw channels 91 in the form of a screw thread and with their central longitudinal axes coaxial with the rotor shaft 30 in the motor housing 1 run. Such a spiral passage 91 serves to transport cooling water. Thus, the motor housing can be large area 1 as well as the housing cover connected to it 2 cool. The engine cooling 90 extends to close to the bearings 50 zoom in, so in the rolling bearings 50 generated heat through the bushings 54 and in the campbooks 54 contacting areas of the motor housing 1 and thus can be registered in the cooling water. The storage cooling 92 is close to the labyrinth seal 70 arranged, causing a cooling of the wall of the motor housing 1 or the housing cover 2 causes the respective compressor wheel 11 . 21 opposite. By means of this cooling can also be a heat dissipation from the compressor wheels 11 . 21 cause. The ring channel 93 the storage cooling 92 extends to at least 20 mm to the bearing bush 54 approach. In preferred embodiments, the distance between bearing bush 54 and the end of the ring channel facing it 93 less than 10 mm, preferably less than 5 mm and particularly preferably 4 mm to 2 mm. For a substantially tightly executed steel or ceramic bushing 54 can the ring channel 93 executed so open be that he reaches the bushing 54 reaches so that the cooling water in direct contact with the bearing bush 54 stands.

By these measures the cooling of the compressor wheels 11 . 21 and the rolling bearing 50 By means of the cooling device, the heat generated by these components dissipate efficiently, so that very high speeds can be realized with the compressor, which leads to an overall increase in the efficiency.

The engine cooling 90 and the storage cooling 92 Be about a first collector 94 fed, as he for example in 3 is shown. From this collector 94 the cooling water becomes the screw passage 91 as well as the respective, the first and second compressor stage 10 . 20 associated ring channels 93 fed. The cooling medium flows from the first collector 94 in the three mentioned cooling points (screw duct 91 , first compressor stage 10 assigned ring channel 93 as well as second compressor stage 20 assigned ring channel 93 ) and from these three cold spots into a second collector 95 from which the cooling medium can be input to the cooling system of a fuel cell and / or an internal combustion engine. That is, the engine cooling according to the invention 90 as well as the integrated storage cooling 92 can be configured as part of an entire, designed for cooling a drive device cooling device.

A special feature of the compressor according to the invention is in particular that of the first compressor stage 10 compressed air via a preferably in the motor housing 1 integrated line of the second compressor stage 20 is supplied. In this case, takes place during transport of the compressed air from the first compressor stage 10 to the second compressor stage 20 cooling the air by means of in 6 illustrated intercooler 100 , The cooling of the compressed air causes a decrease in volume of the first compressor stage 10 compressed gas before entering the second compressor stage 20 , so that with the same power of the electric motor drive of the compressor per unit time more gas volume by means of the second compressor stage 20 can be compressed. This increases the efficiency of the compressor according to the invention. The intercooler 100 is in an advantageous embodiment of the invention as an integral part in the motor housing 1 arranged and heat and in a preferred embodiment also fluidly with the engine cooling 90 coupled, and thus may be part of the cooling device.

Compared to conventional embodiments, therefore, there is no external and separate line for transporting in the first compressor stage 10 compressed air to the second compressor stage 20 provided. By coupling the intermediate cooling 100 with the engine cooling 90 Heat can be absorbed by the first compressor stage 10 compressed gas to the cooling medium of the engine cooling 90 transfer. That is, the engine cooling 90 not only to cool the engine and the rolling bearings 50 is set up, but also directly or indirectly to the cooling of the first compressor stage 10 compressed gas is used. The compressor according to the invention can thus be designed extremely space-saving and operated at the same time with a high efficiency.

The achievable with the two-stage compressor compression ratio is at least 1 bar, in particular 1.5 bar and advantageously above 2 bar. In the above technical dimensions, the compression ratio is in particular 2.6 bar. In this case, the operating conditions are set approximately such that an air entering at a temperature of about 293 Kelvin at the outlet of the first compression stage 10 has a temperature of about 383 Kelvin. About the intercooler 100 will be the one from the first compaction level 10 cooled compressed air to about 333 Kelvin and reached at the output of the second compressor stage 20 after compression in the second compressor stage 20 a temperature of about 389 Kelvin.

When using the compressor according to the invention for the compression of air for supplying to an internal combustion engine of a hybrid vehicle, a renewed cooling in a cooler to the desired operating temperature.

When using the compressor according to the invention for supplying air to fuel cells, in particular in a fuel cell vehicle, no renewed cooling takes place, since the heat generated by the compression in the compressed gas can be utilized by the fuel cells.

When using the compressor according to the invention in an internal combustion engine, in particular in a hybrid vehicle, should by the intercooler 20 as well as by the described downstream of a cooling cooling of at least 20, in particular 30 and preferably 40 Kelvin be realized.

In the 9.1 - 9.4 are the different process steps for the production of in 8th shown rotor shaft 30 shown. 9.1 shows the shaft in delivery condition. Clearly visible are arranged at both ends shaft journals 31 for holding bearings.

In 9.2 the wave is already with a magnet 33 , which is arranged coaxially to the shaft body, as well as with bandages 34 Mistake. The magnet 33 is preferably glued to the shaft body and the bandages 34 are preferably shrunk.

9.3 should symbolize that the magnet 33 along with the bandages 34 the outside is ground to an exact concentricity of the rotor shaft 30 to reach.

Subsequently, as in 9.4 is shown schematically, a reinforcement 35 over the magnet 33 and partly also about the reinforcement 34 preferably arranged by means of shrinking. Between the shaft body of the rotor shaft 30 and the bandage 34 as well as the reinforcement 35 Laser welding can be done, as with the in 9.4 illustrated welding symbols illustrated. The rotor shaft 30 may, optionally after further grinding of the outer reinforcement 35 , in the state shown in the motor housing 1 to be built in.

LIST OF REFERENCE NUMBERS

1

motor housing

2

housing cover

10

First compressor stage

11

First compressor wheel

12

First compressor housing

13

First intake manifold

14

First outlet

20

Second compressor stage

21

Second compressor wheel

22

Second compressor housing

23

Second intake manifold

24

Second outlet

30

rotor shaft

31

shaft journal

32

drilling

33

magnet

34

bandage

35

reinforcement

36

stockists sales

40

temperature sensor

50

roller bearing

51

rolling elements

52

Bearing inner ring

53

Bearing outer ring

54

bearing bush

60

Belleville spring

61

spring washer

62

circlip

70

labyrinth seal

80

bypass

81

compression chamber

82

rotor chamber

90

engine cooling

91

Helical channel

92

Store cooling

93

annular channel

94

First collector

95

Second collector

100

intercooler

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 69425891 T2 [0006]
• DE 20011217 U1 [0008]
• WO 2002/099286 A1 [0009]
• EP 0355796 B1 [0010]
• DE 19814485 A1 [0011]

Claims (16)

A turbocompressor comprising at least one drive unit and at least a first and a second drivable by the drive unit, in each of a first and a second compressor housing ( 12 . 22 ) rotatably arranged compressor wheel ( 11 . 21 ), wherein the first and the second compressor wheel ( 11 . 21 ) are arranged substantially axisymmetrically aligned with each other on a common shaft and the first compressor housing ( 12 ) with at least one gas line fluidly with the second compressor housing ( 22 ) for directing from the first compressor wheel ( 11 ) compressed gas to the second compressor wheel ( 21 ) is connected for recompression, characterized in that at least one intercooler ( 100 ) is arranged, with which the first compressor wheel ( 11 ) and to the second compressor wheel ( 21 ) flowing gas is coolable. Turbo compressor according to claim 1, characterized in that it comprises at least one cooling device for cooling the drive unit, wherein the intercooler ( 100 ) is thermally coupled to the cooling device. Turbo compressor according to at least one of the preceding claims, characterized in that the intercooler ( 100 ) is designed for cooling bearings for the movable storage of moving parts, in particular the while, the turbo-compressor, wherein the intercooler ( 100 ) is thermally coupled to the gas line such that heat of the gas in the gas line in the cooling liquid in the intercooler ( 100 ) is transferable. Turbo compressor according to at least one of the preceding claims, characterized in that on the shaft at least one magnet ( 33 ) is arranged and thus the shaft forms a rotor of an electric motor, wherein the magnet ( 33 ) in the direction of the longitudinal axis of the shaft on both sides by a respective bandage ( 34 ) is secured. Turbo compressor according to claim 4, characterized in that the magnet and the bandages ( 34 ) At least partially overlapping on the shaft, a jacket element is arranged. Turbo compressor according to at least one of the preceding claims, characterized in that the shaft for receiving bearings at both ends in each case a shaft journal ( 31 ), wherein at least in one of the shaft journal ( 31 ) a longitudinal bore is introduced, in which a temperature sensor ( 40 ) is positionable or positioned. Turbo compressor according to at least one of the preceding claims, characterized in that the first compressor wheel ( 11 ) has a diameter which is at least 1/10 larger than the diameter of the second compressor wheel ( 21 ). Turbo compressor according to at least one of claims 2 to 7, characterized in that the cooling device has at least one helical flow channel. Turbo compressor according to at least one of the preceding claims, characterized in that the compressor has at least two bearings for supporting the shaft and the cooling device is configured such that with her in the camps generated heat can be derived. Turbo compressor according to one of the preceding claims, characterized in that the shaft with a configured as a floating bearing and a bearing designed as a bearing bearings ( 50 ) is mounted, wherein the movable bearing in the axial direction by means of at least one plate spring ( 60 ) is clamped. Turbo compressor according to claim 10, characterized in that the disc spring ( 60 ) is arranged such that it in the assembled state between bearing bush ( 54 ) and bearing outer ring ( 53 ) applies substantially the same force on the outer ring of the floating bearing regardless of the thermal expansion of the shaft substantially. Method for compressing gas, in particular air, by means of a turbocompressor, comprising at least one drive unit and at least one first and one second drivable by the drive unit, in each of a first and a second compressor housing ( 12 . 22 ) rotatably arranged compressor wheel ( 11 . 21 ), wherein the first and the second compressor wheel ( 11 . 21 ) are arranged substantially axisymmetrically aligned with each other on a common shaft and the first compressor housing ( 12 ) with at least one gas line fluidly with the second compressor housing ( 22 ) for directing from the first compressor wheel ( 11 ) compressed gas to the second compressor wheel ( 21 ) is connected for recompression, characterized in that the first compressor wheel ( 11 ) in a first consolidation stage ( 10 ) compressed gas through the gas line the second compressor wheel ( 21 ) for the purpose of compaction in a second compaction stage ( 20 ), the gas between the first compression stage ( 10 ) and the second compression level ( 20 ) by means of at least one intermediate cooler ( 100 ) is cooled. A method of compressing gas according to claim 12, characterized in that the turbocompressor is operated at a rotational speed of the shaft which is below the critical rotational speed of the turbocompressor. A fuel cell drive comprising at least one fuel cell for generating electrical energy and a turbocompressor according to at least one of claims 1 to 11 for supplying compressed air to the fuel cell. Internal combustion engine, in particular internal combustion engine as part of a hybrid drive of a motor vehicle, comprising in addition to an internal combustion engine, a turbocompressor according to at least one of claims 1 to 11 for supplying compressed air to the internal combustion engine. Motor vehicle comprising a fuel cell drive according to claim 14 or an internal combustion engine according to claim 15.

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