EXTERNAL GEAR MACHINE

Abstract

The invention relates to an external gear machine (1) in particular an external gear pump or an external gear motor, having at least two gears (3, 4) that mesh with each other in external engagement, wherein the gears (3, 4) are surrounded by a housing (10), wherein one gear (4) has at least one bearing journal (7, 8) and the other gear (3) has a driving or driven journal (5), which are in each case mounted in a bearing bushing (38) so as to respectively be rotatable about a rotation axis (13, 14), wherein a bearing sleeve pp with an anti-twist element is arranged in the bearing bushing (38). In order to improve the external gear machine, in particular with regard to the materials that can be used for producing the bearing bushings and/or the service life, the anti-twist element of the bearing sleeve is arranged in a through-hole of the bearing bushing and is combined with a filter device and/or throttle device via which a working medium of the external gear machine (1) reaches the bearing sleeve.

Description

BACKGROUND OF THE INVENTION

The invention relates to an external gear machine, in particular an external gear pump or an external gear motor, having at least two gears that mesh with each other in external engagement, wherein the gears are enclosed by a housing, wherein the one gear comprises at least one bearing journal and the other gear comprises a driving or driven journal, which are each supported in a respective bearing bush so that they are each rotatable about a respective axis of rotation, wherein a bearing sleeve having a torsional lock is arranged in the bearing bush.

The unexamined German application DE 10 2012 216 254 A1 discloses an external gear machine, in particular a pump or a motor, having a low-pressure connection and a high-pressure connection situated axially opposite one another, having at least two gears that mesh with each other in external engagement, wherein the gears are enclosed by a housing and the one gear comprises a shaft journal and the other gear comprises a driving or driven shaft, which are each supported in a respective bearing bore of a bearing bush, having a substantially rotationally symmetrical cross-section, so that they are each rotatable about a respective axis of rotation, wherein the bearing bushes are received in corresponding seating apertures of the housing, wherein the bearing bushes are composed of aluminum or an aluminum alloy and/or the housing is composed of grey cast iron, wherein the two radially adjacent bearing bushes are each connected to one another to form a double-gland bearing, wherein bearing sleeves, having an axial slot and in which the shaft journal and the driving or driven shaft are rotatably supported, are inserted into the bearing bores of the bearing bushes, wherein the bearing sleeves comprise one or two torsional locking projections, which extend into a locking aperture opening radially into the bearing bore.

SUMMARY OF THE INVENTION

The object of the invention is to improve an external gear machine, in particular an external gear pump or an external gear motor, having at least two gears that mesh with each other in external engagement, wherein the gears are enclosed by a housing, wherein the one gear comprises at least one bearing journal and the other gear comprises a driving or driven journal, which are each supported in a respective bearing bush so that they are each rotatable about a respective axis of rotation, wherein a bearing sleeve having a torsional lock is arranged in the bearing bush, particularly with a view to the materials than can be used for manufacture of the bearing bushes and/or the service life of the external gear machine.

The object is achieved, in the case of an external gear machine, in particular an external gear pump or an external gear motor, having at least two gears that mesh with each other in external engagement, wherein the gears are enclosed by a housing, wherein the one gear comprises at least one bearing journal and the other gear comprises a driving or driven journal, which are each supported in a respective bearing bush so that they are each rotatable about a respective axis of rotation, wherein a bearing sleeve having a torsional lock is arranged in the bearing bush, in that the torsional lock of the bearing sleeve is arranged in a through-hole in the bearing bush and is combined with a filter device and/or restriction device, through which a working medium of the external gear machine reaches the bearing sleeve. The bearing sleeves in the bearing bushes together with the journals rotatably arranged therein represent plain bearings. The bearing sleeves are then also referred to as plain bearing sleeves. The plain bearing sleeves are advantageously pressed into an aluminum bearing bush. The external gear machine is preferably used as an external gear pump in a WHR system, the capital letters WHR standing for the English term Waste Heat Recovery. The WHR system serves for recovering energy from an exhaust gas of a combustion engine in a drivetrain of a motor vehicle. In order to utilize the waste heat from the exhaust gas, a heat exchanger, which transmits the heat from the exhaust gas to a working medium flowing in a heat cycle, is arranged in an exhaust tract of the combustion engine. The working medium in the heat cycle drives an expansion engine. The heat cycle is a thermodynamic working cycle or steam power cycle, which is also referred to as a Rankine cycle or Clausius-Rankine cycle. A continuous-flow machine, for example a turbo machine, or a positive-displacement machine, for example a piston engine, a screw machine or a scroll machine, is used as expansion engine. A condenser and an evaporator are also arranged in the working cycle. The external gear pump is arranged in the working cycle between the condenser and the evaporator. A low-viscosity medium, such as an ORC fluid, is preferably used as working medium in the working cycle. The letters ORC stand for the English term Organic Rankine Cycle. Examples of ORC fluids are ethanol or cyclopentane. In automotive applications the use of a refrigerant, such as is used air-conditioning systems, has proved advantageous. The refrigerant has adequate thermodynamic characteristics and is moreover not inflammable. One disadvantage, however, is that the low-viscosity fluid or medium, for example ethanol, has few, if any, lubricating properties. For this reason, in tests and analyses conducted in the course of the present invention adaptations were made aimed at reducing the bearing stresses. In doing this, for example, the bearing play was reduced and/or the shaft diameter or journal diameter was increased. With the larger shaft diameter or journal diameter, however, a more stable bearing backing is needed. More stable bearing backings or bearing bushes are formed from a steel material, for example, rather than the aluminum material. Combining the torsional lock of the bearing sleeve with the filter device and/or restriction device creates a dual-function part. The dual-function part can serve firstly to reduce the compression of the bearing sleeve in the bearing bush, since an unwanted torsion of the bearing sleeve, resulting from temperature conditions in the bearing and the mechanical bearing stress, for example, is mechanically blocked. Furthermore, the dual-function part can serve for ducting working medium through the bearing bush to the bearing sleeve. The working medium can serve to dissipate frictional heat occurring in the operation of the plain bearing. One particular advantage is that the working medium additionally delivered through the restriction device and/or filter device can improve the build-up of a hydrodynamic lubricating wedge in the plain bearing. Here the filter device and/or restriction device combined with the torsional lock in the dual-function part prevents an unwanted ingress of particles, especially metal chips, into the plain bearing.

A preferred exemplary embodiment of the external gear machine is characterized in that the filter device and/or restriction device combined with the torsional lock comprises a gap filter for the working medium. The gap filtration firstly keeps particles of a risky size away from restriction passages, especially restriction bores, in the bearing sleeve. Furthermore, the gap filtration affords a self-cleaning effect, since the particles are kept outside the bearing bush in the flowing working medium. This means that in a circulating flow the particles can be purposely flushed away with the working medium delivered through the external gear machine.

A further preferred exemplary embodiment of the external gear machine is characterized in that the filter device and/or restriction device combined with the torsional lock comprises a body having at least one flattening, which is arranged in the through-hole in the bearing bush. The body advantageously has substantially the shape of a straight circular cylinder. The flattening on the body allows the passage of working medium. The through-hole in the bearing bush is designed as a bore, for example. The body of the filter device and/or restriction device combined with the torsional lock, for example, is screwed into the through-hole in the bearing bush. The flattening is then advantageously formed as a surface on the engagement thread of the body.

A further preferred exemplary embodiment of the external gear machine is characterized in that the body comprises a torsional lock point at an end facing the bearing sleeve, and a spacer with a filter head at an end remote from the bearing sleeve. The torsional lock point represents a pin, which can be turned into the bearing sleeve, in order to secure this mechanically against rotation in the bearing bush. The torsional lock point is advantageously integrally connected to the body. The spacer is connected to the filter head by a stepped offset. In screwing in or tightening the body, the filter device and/or restriction device combined with the torsional lock is firmly tightened onto the spacer. A desired gap filtration can be set by way of the dimensions or size, in particular the height, of the spacer. The spacer has a height of less than 0.8 millimeter, for example. The spacer and the filter head serve to present a gap for the gap filter. The filter head is advantageously integrally connected to the body by way of the spacer.

A further preferred exemplary embodiment of the external gear machine is characterized in that two radially adjacent bearing bushes are connected to one another to form a double-gland bearing, wherein the filter device and/or restriction device combined with the torsional lock comprises a connecting member, which connects two torsional locking elements to one another and serves for fastening the filter device and/or restriction device combined with the torsional lock to the double-gland bearing. The through-hole is preferably an opening or two openings, which is/are combined with a locating slot, described below, to represent supply channels. The connecting of two radially adjacent bearing bushes to form a double-gland bearing is known in the art. The term radial relates to the axes of rotation of the associated plain bearings. Radial signifies transversely to the axes of rotation. The two torsional locking elements are advantageously integrally connected to one another by the connecting member. This facilitates considerably the handling and assembly of the filter device and/or restriction device combined with the torsional lock. The torsional locking elements, which are preferably integrally connected to the connecting member, are at their free ends advantageously designed as points, which in pressing the connecting member into the locating slot are pushed into the two bearing sleeves as torsional locking.

A further preferred exemplary embodiment of the external gear machine is characterized in that the double-gland bearing comprises a locating slot, which extends between two working medium supply channels through the bearing bushes to the respective bearing sleeve and serves to receive the connecting member with the torsional locking elements. The locating slot is made as a milled slot, for example. A locating gap or milled gap, at least over a part of the length of the locating slot or milled slot, has a fit size for pressing in the connecting member. Here the connecting member advantageously represents a type of taper key, which is driven into the locating slot or milled slot. At its two ends the locating slot is advantageously made somewhat wider, so as to represent the supply channels. The supply channels preferably run along the torsional locking elements. The supply channels easily afford a preferably filtered inflow in the direction of the two bearing sleeves

A further preferred exemplary embodiment of the external gear machine is characterized in that an edge area is bent off from the connecting member which, at least in the area of the supply channels, exercises a gap filter function for the working medium. The connecting member preferably has substantially the shape of an elongated parallelepiped, which is pressed like a taper key into the locating slot of the double-gland bearing. From the underside of the connecting member facing the double-gland bearing, the torsional locking elements extend towards the bearing sleeves in the double-glad bearing. On the upper side of the connecting member remote from the double-glad bearing, the edge area is bent off. The edge area is bent off by flanging, for example. An angle between the bent-off edge area and the connecting member is preferably substantially ninety degrees. In order to represent a gap filter function, the bent-off edge area, at least in the area of the supply channels, is separated by a distance from the double-gland bearing such that a filter gap is produced for the working medium. This is an easy way of preventing an unwanted inflow of particles, for example metal chips, towards the bearing sleeves. A pressing force used to press the connecting member in serves to set the gap height of the filter gap.

A further preferred exemplary embodiment of the external gear machine is characterized in that the edge area bent off from the connecting member between the supply channels represents a limit stop for the filter device and/or restriction device combined with the torsional lock. To form the limit stop, the bent-off edge area, for example the flange, is bent deeper in a middle area. The limit stop serves to facilitate fitting of the filter device and/or restriction device combined with the torsional lock, especially when pressing the connecting member into the locating slot. A height of the middle or more heavily bent flange is an easy way of defining the height of the gap filter. In the area of the supply channels the bent-off edge area is not more heavily bent, in order to maintain the gap filter function.

A further preferred exemplary embodiment of the external gear machine is characterized in that at least one cooling duct, which extends from the through-hole or from the supply channels in the bearing bush to at least one restriction passage in the bearing sleeve, is provided between the bearing sleeve and the bearing bush. The restriction passage in the bearing sleeve is designed as a restriction bore, for example. In the operation of the external gear machine, the heat generated in the plain bearing or in the plain bearings is dissipated outwards via the bearing bush or the bearing bushes. Aluminum bearing bushes or double-gland bearings have a better heat dissipation than, for example, steel bushings. In the tests and analyses conducted in the course of the present invention, at least one cooling duct, which is designed as a scavenging groove, was incorporated into the plain bearing, preferably into the bearing bush, for additional heat dissipation. The cooling duct, especially the scavenging groove, has a very small restriction diameter at its outlet into the bearing sleeve, that is to say at the restriction passage. The restriction diameter is 0.8 millimeter, for example. The filter device and/or restriction device combined with the torsional lock serves to prevent particles, in particular metal chips, being able to reach the restriction passage. An unwanted blockage of the restriction passage, which is also referred to as the scavenging bore, is thereby prevented.

The invention further relates to a filter device and/or restriction device combined with a torsional lock, a bearing bush and/or a double-gland bearing for an external gear machine as previously described. Said parts are marketable separately. The bearing bush or double-gland bearing is advantageously formed from a highly thermally conductive material, such as aluminum. This improves the dissipation of the frictional heat occurring in the operation of the external gear machine and avoids unwanted over-stressing of the plain bearing or plain bearings. Furthermore, the bearing bush or double-gland bearing is advantageously formed from a lightweight material, such as aluminum. This makes the external gear machine lighter. The aluminum material moreover affords the advantage that it is easy to machine, especially in chip-forming metal machining. The bearing bush or double-gland bearing is advantageously produced as a blank in a die casting process. This affords the advantage that some processing steps can be eliminated or shifted directly to the die casting process.

The invention may also relate to a method for the operation and/or manufacture and assembly of an external gear machine as previously described. For example, during a process of running in the external gear machine, material abrasion to the gear tooth crests of the gears of the external gear machine of a housing inner wall, metal chips may be produced in the external gear machine, which could block the restriction passage. This is reliably prevented by the filter device and/or restriction device combined with the torsional lock.

Further advantages, features and details of the invention emerge from the following description, in which various exemplary embodiments are described in detail, referring to the drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

In which:

FIG. 1 shows a schematic representation of the external gear machine with a bearing arrangement, which comprises four plain bearings;

FIG. 2 shows a plain bearing from FIG. 1 in a section through a bearing bush with a torsional lock for the bearing sleeve, wherein the torsional lock is combined with a filter device and/or restriction device;

FIG. 3 shows the enlarged representation of a detail III from FIG. 2;

FIG. 4 shows a perspective representation of the filter device and/or restriction device combined with the torsional lock from FIGS. 1 and 2;

FIG. 5 shows the representation of a section along the line V-V in FIG. 6 through a double-gland bearing with a torsional lock for two bearing sleeves, wherein the torsional lock is combined with a filter device and/or restriction device;

FIG. 6 shows the double-gland bearing from FIG. 5, represented in a top view;

FIG. 7 shows the view of a section along the line VII-VII in FIG. 5;

FIG. 8 shows a detail VIII from FIG. 7;

FIG. 9 shows a perspective representation of the filter device and/or restriction device combined with the torsional lock from FIG. 5, and

FIGS. 10-14 show representations similar to those in FIGS. 5 to 9, according to a further exemplary embodiment, in which a connecting member of the filter device and/or restriction device combined with the torsional lock represents a limit stop.

DETAILED DESCRIPTION

FIG. 1 shows a schematic representation of an external gear machine 1 with a first gear 3 and second gear 4 in a simplified longitudinal section. The externally toothed gears 3, 4 mesh with each other in external engagement.

In FIG. 1 the first gear 3 is rotationally fixed on its left-hand face to a journal 5. If the external gear machine 1 is designed as an external gear pump, the first gear 3 can be driven by the journal 5, which is then also referred to as a drive journal 5. On its right-hand side in FIG. 1 the first or driving gear is rotationally fixed to the bearing journal 6.

The second gear 4 in FIG. 1 laterally has two bearing journals 7, 8, to which the second gear 4 is rotationally fixed. The two gears 3, 4 are rotatably supported in a housing 10 by means of the journals 5, 6 and 7, 8. The first gear 3 is rotatable about a first axis of rotation 13 by means of the drive journal 5 and the bearing journal 6. The second or driven gear 4 is rotatable about a second axis of rotation 14, which is parallel to the first axis of rotation 13, by means of the bearing journals 7, 8.

On its left-hand side in FIG. 1, the housing 10 is bounded by a first housing cover 11, and on its right-hand side in FIG. 1 by a second housing cover 12. A housing body 15 of the housing 10 is arranged between the housing covers 11, 12.

The first housing cover 11 is fixed to the housing body 15 by fixing means 16, 17. The second housing cover 12 is fixed to the housing body 15 by fixing means 18, 19. The fixing means 16 to 19 are dowel pins, for example. The housing covers 11, 12 are connected by means of threaded bolts 81 and washers 82.

In FIG. 1 a first housing gasket 21 is arranged between the first housing cover 11 and the housing body 15. In FIG. 1 a second housing gasket 22 is arranged between the second housing cover 12 and the housing body 15.

In FIG. 1 a radial shaft seal ring 24 serves for sealing a passage through the first housing cover 11 in which the drive journal 5 rotates. The radial shaft seal ring 24 is externally fitted in a known manner into an annular space which extends around the drive journal 5.

In FIG. 1 a bearing arrangement 25 serves to support the two gears 3, 4 in the housing 10. The bearing arrangement 25 comprises two bearings 26, 27 for supporting the first gear 3. The bearing 25 comprises two further bearings 28, 29 for supporting the second gear 4.

Two axial field seals 31, 32, which serve for sealing between the bearings 26, 27 and the housing covers 11, 12, are assigned to the bearings 26 and 27. Two axial field seals 33, 34, which serve for sealing between the bearings 28, 29 and the housing covers 11, 12, are assigned to the bearings 28, 29.

The axial field seals 31 and 33 are advantageously combined in one component. The axial field seals 32 and 34 are likewise advantageously combined in one component. The bearings 26 and 28 are then sealed by the combined axial field seal 31, 33. The bearings 27 and 29 are then sealed by the combined axial field seal 32, 34.

The bearings 26 to 29 of the external gear machine 1 are designed as plain bearings, each having a bearing bush. A bearing sleeve is arranged in the bearing bush. Two radially adjacent bearing bushes may advantageously be connected to one another to form a double-gland bearing.

FIG. 2 represents a plain bearing 36 having a bearing bush 38 in cross-section. The bearing bush 38 in FIG. 2 has a through-hole 39 at the top. The through-hole 39 takes the form of a radial bore, for example.

A bearing sleeve 40 is pressed into the bearing bush 38. Two arrows 41, 42 in FIG. 2 indicate a restriction passage, which takes the form of a restriction bore. The working medium, with which the external gear machine (1 in FIG. 1) is operated, reaches the bearing sleeve 40 via the through-hole 39 in the bearing bush 38. The working medium passes from the through-hole 39 to the restriction bore 41, 42 via at least one cooling duct 54. The through-hole 39, preferably formed as a bore, is connected to a high-pressure duct of the external gear machine, also referred to in brief as a pump, or to the high-pressure duct arranged. This connection or arrangement serves to supply the pump and the plain bearings with fresh medium.

The working medium passes through the restriction bore 41, 42 to the inside of the bearing sleeve 40, where it advantageously improves the build-up of a hydrodynamic lubricating wedge of the plain bearing. Furthermore, by flushing the plain bearing with the working medium heat can be dissipated from the plain bearing 36. For this reason, the restriction bore 41, 42 is also referred to as a scavenging bore. The necessary flushing quantity may be determined by the size of the restriction bore 41, 42. The restriction bore 41, 42 has a diameter of 0.8 millimeter, for example.

A dual-function part 43 is arranged in the through-hole 39 in the bearing bush 38. The dual-function part 43, as can be seen in FIG. 3, combines a torsional lock 44 for the bearing sleeve 40 with a filter device and/or restriction device 45 for the working medium entering the through-hole 39. The filter device/and/or restriction device combined with the torsional locking device comprises a body 46, which substantially has the shape of a straight circular cylinder with an external thread.

From the body 46 a pin having a torsional lock point 47 extends downwards in FIG. 3. The body 46 is screwed into the through-hole 39 in the bearing bush 38, so that the torsional lock point 47 is pressed out into the bearing sleeve 40. The bearing sleeve 40 is thereby held in position, secured against torsion, in the bearing bush 38.

It will be seen in FIGS. 3 and 4 that the body 46 of the dual-function part 43 is integrally connected to a filter head 49 by a spacer 48. The spacer 48 has substantially the shape of a circular disk with a flattening, not further identified, which merges into a flattening 50 of the body 46.

The spacer 48 in combination with the filter head 49 serves to represent a filter gap 51, 52. In FIG. 3 particles, which collect in front of the filter gap 51, 52, are indicated at 53. A suitable size, in particular the height, of the filter gap 51, 52, prevents the particles 53 passing through the through-hole 39 in the direction of the bearing sleeve 40. The working medium passes without the particles 53 through the filter gap 51, 52 along the flattening 50 into the cooling duct 54.

FIGS. 4 and 5 show two exemplary embodiments of two plain bearings 56, 57, in which two bearing bushes 58, 59 are combined in a double-gland bearing 60. A bearing sleeve 61 is arranged in the bearing bush 58. A bearing sleeve 62 is arranged in the bearing bush 59. The two bearing bushes 58, 59 are integrally connected to one another by the double-gland bearing 60.

A dual-function part 63, in which a torsional lock is combined with a filter device and/or restriction device 86, is assigned to the double-gland bearing 60. Here too, the torsional lock 63 is fitted into the high-pressure area of the external gear machine, also referred to in brief as a pump, in order to supply the plain bearings with fresh medium from the high pressure. The torsional lock comprises two torsional locking elements 66,67, which are integrally connected to one another by a connecting member 65. At a free end, the bottom end in FIG. 5, the torsional locking element 66 has a point 68, which is pressed into the bearing sleeve 61 to secure it against torsion. Similarly, at a free end, the bottom end in FIG. 5, the torsional locking element 67 has a point 69, which is pressed into the bearing sleeve 62 to secure it against torsion.

The dual-function part 63 is pressed or jammed with the connecting member 65 into a locating slot 70. The locating slot 70 takes the form of a milled slot, for example, and extends between two supply channels 71, 72. The supply channel 71 runs along the torsional locking element 66 to the bearing sleeve 61. The supply channel 72 runs along the torsional locking element 67 to the bearing sleeve 62. The supply channels 71, 72 open into cooling ducts 73, 74. The cooling duct 73 connects the supply channel 71 to a restriction passage 75. The cooling duct 74 connects the supply channel 72 to a restriction passage, indicated by arrows 76, 77.

The cooling ducts 73, 74, as will be seen in particular in FIGS. 5 and 6, are designed as helical scavenging grooves 79, 80. The helical scavenging grooves 79, 80 are introduced radially into the bearing bushes 58, 59 and serve to carry the working medium of the external gear pump (1 in FIG. 1). The cooling of the bearing sleeves 61, 62 is thereby significantly improved. The working medium from the helical scavenging grooves 79, 80 passes through the restriction passages 75, 76, 77 to the inside of the bearing sleeves 61, 62, where it serves to build up the hydrodynamic lubricating wedge in the plain bearings 56, 57.

An edge area 85 remote from the double-gland bearing 60 in FIG. 5 is bent off from the connecting member 65 in order to represent a gap filter of the filter device and/or restriction device 86. A gap height for the gap filtration is indicated by arrows 87, 88 in FIG. 8. Particles, the unwanted ingress of which into the helical scavenging grooves 79, 80 is prevented by the filter device and/or restriction device 86, are indicated at 90,

In the assembly process the connecting member 65 is pressed into the locating slot 70. The locating slot 70 has a press-fit over its length for pressing in the connecting member 65. The locating slot 70 is designed somewhat wider close to its two ends, in order to form the supply channels 71, 72.

It can be seen in FIG. 9 that the two points 68, 69 are integrally connected to the bent-off edge area 85 by the connecting member 65. To form the bent-off edge area 85, the connecting member 65 is flanged on its upper edge. The gap height (87, 88 in FIG. 8) can be set by way of the pressing force used to press in the connecting member 65 of wedge-shaped cross-section.

The exemplary embodiment represented in FIGS. 10 to 14 very largely corresponds to the exemplary embodiment represented in FIGS. 5 to 9. For this reason, the same reference numerals are used to denote identical or similar parts. In order to avoid repetition, reference is made to the preceding description of FIGS. 5 to 9. Only the differences between the two exemplary embodiments are examined below

In the exemplary embodiment represented in FIGS. 10 to 14 the edge area 85 of the connecting member 65, bent-off as flanging, is bent deeper, in order to represent a limit stop when fitting the dual-function part 63. This means that the gap height no longer depends on the pressing force when pressing the connecting member 65 into the locating slot 70, as previously described. The height of the more heavily bent flanging in the middle portion 100 serves to set or determine the gap height (87, 88 in FIG. 13). In two end portions 101, 102 the edge area 85 is separated by the gap height (87, 88 in FIG. 13) from the double-gland bearing 67, in order to represent the gap filter function.

Claims

1. An external gear machine (1), having at least first and second gears (3,4) that mesh with each other in external engagement, wherein the gears (3,4) are enclosed by a housing (10), wherein the second gear (4) comprises at least one bearing journal (7,8) and the first gear (3) comprises a driving or driven journal (5), wherein the bearing journal and the driven journal are supported in respective bearing bushes (38;58,59) so that the bearing journal and the driven journal are rotatable about respective axes of rotation (13,14), wherein bearing sleeves (40;61,62) having respective torsional locks (44;65,66) are arranged in respective ones of the bearing bushes (38;58,59), characterized in that the torsional lock (44;65,66) of each of the bearing sleeves (40;61,62) is arranged in a through-hole (39;70) in the associated bearing bush (38;58,59) and is combined with a filter device and/or restriction device (45;86) through which a working medium of the external gear machine (1) reaches the bearing sleeve (40;61,62).

2. The external gear machine as claimed in claim 1, characterized in that the filter device and/or restriction device (45;86) combined with the torsional lock (44;65,66) comprises a gap filter for the working medium.

3. The external gear machine as claimed in claim 1, characterized in that the filter device and/or restriction device (45) combined with the torsional lock (44) comprises a body (46) having at least one flattening (50), which is arranged in the through-hole (39) in the bearing bush (38).

4. The external gear machine as claimed in claim 3, characterized in that the body (46) comprises a torsional lock point (47) at an end facing the bearing sleeve (40), and a spacer (48) with a filter head (49) at an end remote from the bearing sleeve (40).

5. The external gear machine as claimed in claim 1, characterized in that two radially adjacent bearing bushes (58,59) are connected to one another to form a double-gland bearing (60), wherein the filter device and/or restriction device (86) combined with the torsional lock comprises a connecting member (65), which connects two torsional locking elements (66,67) to one another and serves for fastening the filter device and/or restriction device (86) combined with the torsional lock to the double-gland bearing (60).

6. The external gear machine as claimed in claim 5, characterized in that the double-gland bearing (60) comprises a locating slot (70), which extends between two working medium supply channels (71,72) through the bearing bushes (58,59) to the respective bearing sleeve (61,62) and serves to receive the connecting member with the torsional locking elements (66,67).

7. The external gear machine as claimed in claim 5, characterized in that an edge area (85) is bent off from the connecting member (65) which, at least in the area of the supply channels (71,72), exercises a gap filter function for the working medium.

8. The external gear machine as claimed in claim 7, characterized in that the edge area (85) bent off from the connecting member (65) between the supply channels (71,72) represents a limit stop (100) for the filter device and/or restriction device (86) combined with the torsional lock.

9. The external gear machine as claimed in claim 6, characterized in that at least one cooling duct (54;73,74), which extends from supply channels (71,72) in the bearing bush (38;58,59) to at least one restriction passage (41,42;75,76,77) in the bearing sleeve (40;61,62), is provided between the bearing sleeve (40;61,62) and the bearing bush (38;58,59).

10. (canceled)

11. The external gear machine as claimed in claim 1, characterized in that at least one cooling duct (54;73,74), which extends from the through-hole (39;70) in the bearing bush (38;58,59) to at least one restriction passage (41,42;75,76,77) in the bearing sleeve (40;61,62), is provided between the bearing sleeve (40;61,62) and the bearing bush (38;58,59).