WO2016000935A1

WO2016000935A1 - Electrical compressor for an internal combustion engine

Info

Publication number: WO2016000935A1
Application number: PCT/EP2015/063197
Authority: WO
Inventors: Stefan Rothgang; Sven Nigrin; Hendrik Ferner; Andreas Burger
Original assignee: Pierburg Gmbh
Priority date: 2014-07-02
Filing date: 2015-06-12
Publication date: 2016-01-07
Also published as: DE102015106643A1

Abstract

Electrical compressors for internal combustion engines having a multipartite housing (10, 12, 30, 38) in which a flow space (36) with an inlet (44) and an outlet and also an engine compartment (32) are formed, an electric motor (16) with a drive shaft (20) which is arranged in the engine compartment (32) of the housing (10, 12, 30, 38), an impeller (34) which is fastened on the drive shaft (20) of the electric motor (16) and is arranged in the flow space (36), two bearings (22, 26) by means of which the drive shaft (20) of the electric motor (16) is mounted, two bearing receptacles (24, 28) which are formed in the housing (10, 12, 30, 38) and in which the two bearings (22, 26) are arranged, wherein the housing (10, 12, 30, 38) has a base (40, 90) which extends radially in relation to the drive shaft (20) and from the centre of which a cylindrical projection (54, 88), which serves as a bearing receptacle (24, 28), extends axially into the engine compartment (32) and from which a side wall (64, 82) which surrounds the cylindrical projection (54, 88) around the entire periphery axially extends, are known. In order to improve the rigidity of the housing and to ensure increased precision in respect of the position of the bearings even at high rotation speeds, it is proposed according to the invention that the side wall (64, 82) and the cylindrical projection (54, 88) are connected to one another by ribs (62, 86) which extend axially into the engine compartment (32).

Description

DESCRIPTION

Electric compressor for an internal combustion engine

The invention relates to an electric compressor for an internal combustion engine having a multi-part housing in which a flow space with an inlet and an outlet and an engine compartment are formed, an electric motor with a drive shaft which is arranged in the engine compartment of the housing, an impeller which on the Drive shaft of the electric motor is fixed and is arranged in the flow space, two bearings, via which the drive shaft of the electric motor is mounted, two bearing receptacles which are formed in the housing and in which the two bearings are arranged, wherein the housing has a radially extending to the drive shaft bottom has, from which extends centrally a cylindrical projection which serves as a bearing receptacle, axially into the engine compartment and from which extends axially a side wall which surrounds the cylindrical projection in full.

Such electric compressors are used in modern internal combustion engines, in order to be able to provide a sufficient boost pressure in the short term, for example, in the event of sudden load increase demand. Particularly in internal combustion engines with a small displacement and high power, these electric compressors in the region close to the idling either enable additional recompression to the exhaust-gas turbocharger or precompression for the latter, whereby the so-called turbocharger can be counteracted. Also, the use is possible as a single supercharger in the internal combustion engine. The rotor and thus the impeller of such a used compressor must be accelerated in no time to speeds of up to 100,000 rev / min. At these speeds, high radial and axial forces arise, which must be absorbed by the bearings and the housing in which the bearings are arranged in order to reduce vibrations of the housing and thus also to improve the rotor guidance. In most cases roller bearings, in particular ball bearings are used for storage in such compressors, which are arranged in corresponding bearing receptacles of the housing.

Such an electric compressor is known for example from DE 11 2012 002 973 T5. The drive shaft of the electric motor, on which the impeller of the compressor is mounted, is mounted in the direction of an engine compartment extending cylindrical projections over two ball bearings. Each of these projections is centrally formed on a motor space axially delimiting bottom, which are each formed on a housing part and are inserted into one another during assembly. However, at high speeds, large vibration occurs due to the low rigidity of the housing and the projections.

It is therefore an object to provide an electric compressor with which the axial and radial forces are absorbed so that vibrations of the housing and the bearing mounts are reduced, whereby the life of the bearing and the compressor is increased. Damage to the bearings and the impeller or the drive shaft to be reliably prevented by a precise guidance of the shaft and alignment of the bearings, which are maintained even at high speeds of the electric motor by avoiding the vibrations. At the same time both the space used and the weight should be kept as low as possible.

This object is achieved by an electric compressor with the features of the main claim 1. Characterized in that the side wall and the cylindrical projection are connected by extending axially into the engine compartment ribs, the rigidity of the bearings and the surrounding housing is increased, whereby rotation of the rotor in natural frequency position of the housing is avoided, so that damage to the bearings and be reliably avoided on the shaft or the impeller, since at high speeds no alignment or misalignment due to vibrations of the housing arise.

Preferably, the housing has a first housing part, in which the first cylindrical projection with the ribs and the side wall are formed and a second housing part, which has a second radially extending to the drive shaft bottom, of which centrally a second cylindrical projection, serves as a second bearing receptacle and a second side wall which completely surrounds the cylindrical projection, extend axially into the engine compartment, wherein the side wall and the cylindrical projection are connected by axially extending into the engine compartment ribs and the side wall of a housing part, the side wall of the radially surrounds other housing part. Such an embodiment increases the rigidity of the entire housing and the second bearing.

In one embodiment of the invention, one of the bearings serves as a fixed bearing and one of the bearings as a floating bearing and both bearings are designed as rolling bearings. In this way, a storage is provided with low wear and low cost, which is insensitive to thermal expansion.

It is advantageous if the electric motor has a rotor and a stator wound with stator teeth, wherein the stator is attached to the side wall of a housing serving as a motor housing part. The connection can in particular by pressing the stator in one of Housing parts are manufactured, so that no additional components are needed.

In a particularly preferred embodiment of the invention, the number of stator teeth corresponds to the number of ribs of the motor housing, wherein the ribs are arranged in the circumferential direction between each two stator teeth and extending between arranged on the stator teeth windings, whereby the axially required space is minimized. Since the coil ends can be led to the bottom of the housing parts. Nevertheless, an increased rigidity of the housing is produced. Nevertheless, a clearance of the winding heads is preserved.

In a further embodiment, the axial height of the ribs at the end facing the cylindrical projection is greater than in a region opposite to the stator. This design also shortens the required axial space and on the other hand leads to increased stability and rigidity of extending into the engine compartment bearing mounts.

A particularly high rigidity of the bearing mounts is achieved when the height of the ribs in the area adjacent to the cylindrical projection corresponds to the height of the cylindrical projection, whereby guiding and alignment errors due to vibrations at high speeds due to the stiff waveguide are largely excluded.

It is advantageous if the height of the ribs grows parabolic from the area opposite the stator to the cylindrical projection, so that the height of the ribs resembles the shape of the wound stator teeth and in this way optimally utilizes the existing installation space to increase the rigidity of the housing. It will In particular, the rigidity of the bearings and the floors, increased with minimized weight.

These advantages also arise for the area of the radially outer side walls when the height of the ribs from the area opposite the stator to the side wall grows. Thus, a high rigidity of the mating outer sidewalls is created.

In a preferred embodiment, the ribs on the end pointing to the second cylindrical projection are formed as annular projections with internal passage openings through which project the ends of the windings of the stator. This simplifies the contacting of the stator windings without reducing the rigidity of the housing.

Preferably, the second housing part has an annular receiving opening which is bounded radially inwardly by the side wall of the second housing part and is bounded radially outwardly by an axially extending peripheral wall, which the side wall of the motor housing, whose end is arranged in the annular receiving opening, radially surrounds. This facilitates assembly and leads by the pairing of the two housing parts to a stiffening of the overall housing. Vibrations of the axial side wall end are thus avoided, since this is held in the region of the stabilized by the ribs side wall of the second housing part.

An additional stiffening experienced by the housing in that the motor housing on the outside of the side wall has a helically extending around the side wall web against which the peripheral wall of the second housing part bears radially. On the one hand, this web increases the rigidity of the motor housing and, due to the abutment of the circumferential wall, additionally ensures a rigidity of the second housing part that is increased in the installed state. Furthermore, the arising free spaces between the webs to the coolant guide and thus used to cool the voltage applied to the housing part stator windings.

There is thus provided an electric compressor for an internal combustion engine, which has a long life due to increased rigidity of the entire housing including the bearings. The required space is minimized as well as the required amount of material and thus the weight. Due to the increased rigidity of the bearing points of the housing bases and the side walls, the axial and radial forces occurring at high rotational speeds can be reliably absorbed without fear of misalignment or guiding errors of the shaft. Accordingly, the leadership of the drive shaft and the rotor and the impeller can be ensured with high precision even at high speeds.

An embodiment of an electric compressor according to the invention is shown in the figures and will be described below.

Figure 1 shows a side view of an electric compressor according to the invention in a partially sectioned illustration.

Figure 2 shows a perspective view of the first housing part of the electric compressor shown in Figure 1.

FIG. 3 shows a perspective view of the second housing part of the electric compressor shown in FIG.

The electric compressor according to the invention consists of a housing 10, which is composed of a total of four housing parts. A first central housing part 12 forms the motor housing, in which a stator 14 of an electric motor 16 is pressed. This stator 14 acts in a known manner with a rotor 18 which is fixedly mounted on a drive shaft 20. The drive shaft 20 is connected via a first designed as a ball bearing 22, which is arranged in a first bearing receptacle 24 which is formed centrally on the motor housing 12, and a second designed as a ball bearing 26, which is arranged in a second bearing receptacle 28, the centrally is formed on a second housing part 30, which serves as an electronics housing stored. The motor housing 12 and electronics housing 30 define an engine compartment 32 in which the entire electric motor 16 is received.

On the drive shaft 20, an impeller 34 of the electric compressor is arranged, which is arranged in a flow space 36, which is bounded by a flow housing 38 and a first radially extending to the drive shaft 20 bottom 40 of the motor housing 12. The flow housing 38, which is fastened to the motor housing 12, has a spiral channel 42 into which the gas flowing in via an inlet 44 formed on the flow housing 38 is conveyed by means of the impeller 34. In the spiral channel 42, this gas is compressed until it leaves the flow space 36 and the spiral channel 42 via an outlet also formed on the flow housing 38, not shown.

In order to separate the flow space 36 from the engine compartment 32 as gas-tight as possible and to prevent gas flowing from the flow housing 38 into the motor housing 12 at the rear of the impeller 34 along the drive shaft 20, is in a central opening 48 of the bottom 40 of the motor housing 12, which has the impeller 34, a mechanical seal 50 which abuts against a constriction 52 of this opening 48 axially. On the side facing the engine compartment 32 side of the constriction 52 extends from the bottom 40, a cylindrical projection 54 axially in the direction of the rotor 18. This cylindrical projection 54 serves as a first bearing seat 24 for the first bearing 22, the inner ring 56 itself on the one hand abuts against the mechanical seal 50 and on the other hand against a shaft shoulder 58 and the outer ring 60 abuts against the constriction 52.

According to the invention, this cylindrical projection 54 is connected via ribs 62 to a cylindrical side wall 64, which radially borders the engine compartment 32 and extends axially from the bottom 40 in the direction of the electronics housing 30, to the inside of which the stator 14 is pressed. In the present embodiment, the motor housing 12 has six ribs 62 whose height changes in the axial direction approximately parabolic. The height of the ribs 62 at the radially inner region connected to the cylindrical projection 54 corresponds to the axial extent of the cylindrical projection 54. The stator 14 also has six stator teeth 66 on which windings 68 for energizing the electric motor 16 are arranged. The winding heads of these windings 68 extend until just in front of the bottom 40. In order nevertheless to be able to achieve stiffening of the motor housing 12 by the ribs 62, the ribs 62 are each offset relative to the windings 68 of the stator teeth 66. The ribs 62 thus extend, viewed in the circumferential direction, exactly between the windings 68 into the free spaces present there. The axial height of the ribs 62 is to minimize the space required in a winding 68 axially axially opposite portion 70 least and grows radially in the direction of the cylindrical side wall 64th

On the outside of the side wall 64, a helical web 72 is formed, against the radial outer side of an axially extending cylindrical peripheral wall 74 of the electronics housing 30 is applied, so that between the turns of the web 72, a channel 76 is formed, which is flowed through by a coolant. Accordingly, the side wall 64 of the motor housing 12 is surrounded over the entire axial extent of the stator 14 of the electric motor 16. To seal this channel 76 is pointing to the flow housing 38 axial end of the Circumferential wall 74 a arranged between the peripheral wall 74 and the side wall 64 of the motor housing 12, a seal 78. The axial end of the side wall 64 is disposed in an annular receiving opening 80 which is formed radially between the peripheral wall 74 and a cylindrical second side wall 82 of the electronics housing 30, wherein between the side wall 82, which extends axially in the direction of the flow housing 38, and Side wall 64 of the motor housing 12 at the gasket 78 opposite axial end of the channel 76 is also a seal 84 for sealing the channel 76 is arranged.

This side wall 82 of the electronics housing 30, as well as the side wall 64 of the motor housing 12 via six second, radially and axially extending ribs 86 with an axially into the engine compartment 32 facing second cylindrical projection 88 is connected. This serves as a second bearing receptacle 24 for the second ball bearing 26 and is integrally formed with a second radially extending bottom 90, from which also the peripheral wall 74 and the side wall 82 extend axially. As can be seen in FIG. 3, the ribs 86 extend in the axial direction in the region of the side wall 82 over their entire axial extent. Towards the cylindrical projection 88 inwardly, this extension sinks approximately parabolically, so that once again the axial height is lower in the region opposite the winding 68. Again, the ribs 86 are circumferentially between the stator teeth 66. In the radially inner region, the ribs 86 instead of narrow webs as annular projections 92 are formed with an inner through hole 94, through which one winding end of each winding 68 to the opposite side of the floor 90 extends. On this rear side of the bottom 90, a circuit board 96 is arranged, which contains the control electronics, so that the coil ends can be connected directly to the circuit board 96 and the windings 68 are supplied via the circuit board 96 with power can to drive the electric motor 16. The circuit board 96 is located in an electronics compartment 98 which is radially bounded by an outer wall 100 extending to the peripheral wall 74 from the bottom 90 and is axially closed by a cover 102.

The second bearing 26 is designed as a floating bearing, so that thermal expansion can be compensated. This second ball bearing 26 rests with its inner ring 104 against a shoulder of the drive shaft 20. Its outer ring 106 is loaded by means of a spring assembly 108 with the interposition of a ring 110 in the direction of this paragraph. On the inner wall of the cylindrical projection 88, a groove 112 is formed, in which an O-ring 114 is arranged, which rests against the outer ring 106 of the bearing 26 outside and thus seals the gap.

The design of the housing 10 and in particular of the two housing parts 12, 30 with the ribs 62, 86 leads to a very good rigidity of the housing 10 and the bearing receivers 24, 28. Additional stability is also provided by the web 72 and the arrangement and attachment of the housing parts 12, 30 generated to each other. This high stiffness means that at rotational speeds of the impeller 34 of up to 80,000 rev / min, the resulting axial and radial forces can be absorbed by the housing 10 and the natural frequency position of the rotor 18 is shifted to higher speeds, resulting in excessive vibrations of the compressor be avoided as far as possible. Instead, it is possible to arrange both rolling bearings 22, 26 exactly aligned with each other and to ensure a corresponding precise guidance of the drive shaft 20. Nevertheless, the material consumption and the required installation space due to the arrangement of the ribs 62, 86 is reduced.

It should be clear that the scope of the main claim is not limited to the embodiment described. In particular, the housing parts may have other pitches or the shape of the Ribs are meaningfully changed. Other design changes are also conceivable.

Claims

An electric compressor for an internal combustion engine having a multi-part housing (10, 12, 30, 38) in which a flow space (36) with an inlet (44) and an outlet and an engine compartment (32) are formed, an electric motor ( 16) having a drive shaft (20) which is arranged in the engine compartment (32) of the housing (10, 12, 30, 38), an impeller (34) which is mounted on the drive shaft (20) of the electric motor (16) and is arranged in the flow space (36), two bearings (22, 26), via which the drive shaft (20) of the electric motor (16) is mounted, two bearing receptacles (24, 28) in the housing (10, 12, 30, 38 ) are formed and in which the two bearings (22, 26) are arranged, wherein the housing (10, 12, 30, 38) has a radially to the drive shaft (20) extending bottom (40, 90), from which itself centrally a cylindrical projection (54, 88) which serves as a bearing receptacle (24, 28) extends axially into the engine compartment (32) and of the a side wall (64, 82) which completely surrounds the cylindrical projection (54, 88) extends axially, characterized in that the side wall (64, 82) and the cylindrical projection (54, 88) extend axially into one another Engine compartment (32) extending ribs (62, 86) are interconnected. An electric compressor for an internal combustion engine according to claim 1, characterized in that the housing (10, 12, 30, 38) comprises a first housing part (12) in which the first cylindrical projection (54) is formed with the ribs (62) and a second housing part (30) having a second radially to the drive shaft (20) extending bottom (90) from which centrally from a second cylindrical projection (88) serving as a second bearing receptacle (28) and a second side wall (82) which completely surrounds the cylindrical projection (88) extends axially into the engine compartment (32), the side wall (82) and the cylindrical projection (88) being formed by ribs (86) extending axially into the engine compartment (32). are interconnected and the side wall (64) of the one housing part (12), the side wall (82) of the other housing part (30) radially surrounds. An electric compressor for an internal combustion engine according to claim 1 or 2, characterized in that one of the bearings (22) serves as a fixed bearing and one of the bearings (26) serves as a floating bearing and both bearings (22, 26) are formed as rolling bearings. An electric compressor for an internal combustion engine according to any one of the preceding claims, characterized in that the electric motor (16) comprises a rotor (18) and a stator (14) with wound stator teeth (66), the stator (14) being fixed to the side wall (64) ) of the motor housing serving as the housing part (12) is attached. An electric compressor for an internal combustion engine according to claim 4, characterized in that the number of stator teeth (66) corresponds to the number of ribs (62) of the motor housing (12), the ribs (62) viewed in the circumferential direction in each case between two stator teeth (66). are arranged and extend between arranged on the stator teeth (66) windings (68). An electric compressor for an internal combustion engine according to any one of the preceding claims, characterized in that the axial height of the ribs (62) is greater at the end facing the cylindrical projection (54) than in an area opposite the stator (14). An electric compressor for an internal combustion engine according to claim 6, characterized in that the height of the ribs (62) in the area adjacent to the cylindrical projection (54) corresponds to the height of the cylindrical projection (54). An electric compressor for an internal combustion engine according to any one of claims 4 to 7, characterized in that the height of the ribs (62) from the stator (14) opposite region to the cylindrical projection (54) grows parabolic. An electric compressor for an internal combustion engine according to any one of claims 4 to 8, characterized in that the height of the ribs (62, 86) from the stator (14) opposite region to the adjacent side wall (64, 82) grows. An electric compressor for an internal combustion engine according to any one of the preceding claims, characterized in that the ribs (86) are formed at the second cylindrical projection (88) facing end as annular projections (92) having inner through holes (94) through the ends the windings (68) of the stator (14) protrude.

1. An electric compressor for an internal combustion engine according to any one of the preceding claims,

characterized in that

the second housing part (30) has an annular receiving opening (80) which is bounded radially inwardly by the side wall (82) of the second housing part (30) and is bounded radially outwardly by an axially extending peripheral wall (74) defining the Side wall (64) of the motor housing (12), whose end is arranged in the annular receiving opening (80), radially surrounds.

2. An electric compressor for an internal combustion engine according to claim 10,

characterized in that

the motor housing (12) on the outside of the side wall (64) has a helically around the side wall (64) extending web (72) against which the peripheral wall (74) of the second housing part (30) bears radially.