Hydrostatic displacement unit with a central housing section in which bearings for two separate drive shafts are arranged

Abstract

Hydrostatic displacement unit (1) with at least three hydrostatic drive units (34, 36, 38) which are connected in a rotationally fixed manner to a drive shaft arrangement (20, 40) and arranged in series along the latter, and which each have at least one hydrostatic working chamber which is fluidically connectable alternately to a high-pressure chamber (24, 26, B) and to a low-pressure chamber (22, 28, A) of the displacement unit (1), wherein a last one (38) of the drive units (34, 36, 38) in the series is cantilevered, wherein the drive shaft arrangement (20, 40) has at least two drive shafts (20, 40) which are at least partially decoupled with respect to their operational bending and which are each rotatably mounted via two bearing points (84, 86, 92, 94) and substantially independently of one another, and with a housing (8) with three pot-shaped housing parts (10, 12, 14), each having a housing base (54, 56, 58) and a housing base (54, 56,58) have a housing opening (60, 62, 64) arranged substantially opposite one another, wherein the last drive unit (38) is accommodated at least partially or completely in an interior space of a last (14) of the housing parts (10, 12, 14) in the row, a central (36) of the drive units (34, 36, 38) is accommodated in an interior space of a central (12) of the housing parts (10, 12, 14) in the row, and a first (34) of the drive units (34, 36, 38) is accommodated in an interior space of a first (10) of the housing parts (10, 12, 14) in the row, characterized in that one (84, 92) of the bearing points (84, 86, 92, 94) of each of the two drive shafts (20, 40) is arranged on the housing base (56) of the central housing part (12).

Description

The invention relates to a hydrostatic displacement unit according to the preamble of claim 1.A displacement unit of the generic type is shown in U.S. Pat. No. 3,426,686 A, in which hydrostatic power units of three hydraulic pumps are combined in one housing. Each of the engines is connected to one of two drive shafts of a drive shaft arrangement. The two drive shafts are likewise connected to one another in a rotationally fixed manner. A first of the engines is part of a variable displacement hydraulic pump (main pump) designed in swashplate construction. A central and a last of the engines are each part of an internal gear pump. The last internal gear pump provides control pressure means for adjusting the axial piston machine, the central internal gear pump prestresses a low-pressure side of the axial piston pump to a required charge pressure.The displacement unit has a three-part housing, wherein a bearing point for mounting the drive shaft arrangement is provided on each of the housing parts. A central one of the bearing points is formed in the central housing part and is arranged in a region in which the two drive shafts are connected in a rotationally fixed manner. The first drive mechanism is arranged between a first of the bearing points and the middle bearing point, and the second and third drive mechanisms are arranged between the middle bearing point and a last of the bearing points.The disadvantage of the design of the displacement unit is, on the one hand, its long overall length in the direction of the drive shafts. In addition, it has proved difficult to mount the last, pot-shaped housing part in which the last drive mechanism is accommodated.DE 33 07 790 A1 discloses a hydrostatic displacement unit with two separate drive shafts. The drive shafts are connected to one another in a rotationally fixed manner via a toothing. The one drive shaft is assigned an engine of axial piston construction. The other drive shaft is assigned three drive mechanisms, which are each designed as internal gear units. Both drive shafts are each mounted at two bearing points. This hydrostatic displacement unit has a great length in the direction of the axis of rotation of the drive shafts.In contrast, the object of the invention is to create a hydrostatic displacement unit which is shorter in the direction of the drive shafts and / or which is easier to install.This object is achieved by a hydrostatic displacement unit having the features of claim 1.Advantageous refinements of the displacement unit are described in patent claims 2 to 10.A hydrostatic displacement unit has at least three hydrostatic power units which are arranged in a rotationally fixed connection with a drive shaft arrangement of the displacement unit and along the latter in series. Each of the engines has at least one hydrostatic working space, by means of which mechanical rotational energy can be converted into hydrostatic pressure energy. The at least one hydrostatic working chamber can be fluidically connected alternately to a high-pressure chamber and to a low-pressure chamber of the displacement unit. Preferably, each of the engines is assigned a different high-pressure chamber and a different low-pressure chamber of the displacement unit. According to the invention, a last one of the engines in the row, in particular one of the engines that can be mounted last in an assembly sequence, is mounted in a floating manner.The design of the flying bearing provides the advantage that the hydrostatic displacement unit can be of shorter construction compared to the state of the art to be considered. In addition, the assembly capability of the last of the engines is simpler due to its flying mounting. In addition, the third of the engines can be mounted via two already existing bearing points provided for other of the engines. The flying bearing arrangement thus leads to a saving in a bearing point / bearing device, as a result of which the displacement unit can be mounted in a simpler manner in terms of device technology and with less outlay. Due to the flying bearing arrangement, the displacement unit according to the invention also advantageously has a tolerance chain of a similar short length to that of a displacement unit having only two engines, both of which are each mounted between two bearing points. This also has a favourable effect on assembly costs and a quality of the displacement unit.In a preferred development, the last of the engines or the last and a central of the engines is in each case that of an internal gear machine or a ring gear machine or a vane cell machine of the displacer unit. A first of the engines in the row is preferably that of an axial piston machine, preferably that of a swashplate construction with adjustable stroke volume. Compared to the internal gear and ring gear machine, a vane cell machine has the advantage that it can be designed with a constant or adjustable stroke volume.According to the disclosure, the displacement unit has a housing with at least three pot-shaped housing parts, each of which has a housing base and a housing opening arranged substantially opposite the housing base. In this case, the last drive mechanism is accommodated in an interior of a last of the housing parts in the row, and a central of the drive mechanisms is accommodated in an interior of a central of the housing parts in the row, and a first of the drive mechanisms is accommodated in an interior of a first of the housing parts in the row, at least in sections, but particularly preferably completely.The pot-shaped housing parts arranged in series facilitate mounting of the displacement unit in particular when, in a preferred development, the housing opening of the central housing part is closed at least in sections via the housing bottom of the last housing part and the housing opening of the first housing part is closed via the housing bottom of the central housing part.In order that the drive shaft arrangement can be connected to all three engines in a rotationally fixed manner, in a preferred refinement, the housing bases each have a through-recess through which the drive shaft arrangement passes.For closing the housing in a pressure-medium-tight manner, the displacement unit has a housing cover, by which the housing opening of the last housing part is closed. Preferably, a suction connection and a pressure connection of the last engine, which can be supplied with pressure medium via it and is arranged adjacent to it, are formed on the housing cover.A particularly compact construction, by means of which a plurality of flanges between the housing parts can be dispensed with, and by means of which the assembly can be carried out with only a few connecting processes, the three housing parts are connected to one another by means of a plurality of screws passing through at least the last and the central housing part. The screws can also pass through the first of the housing parts or can be screwed therein only in sections.In a preferred development, the housing cover is also penetrated by the screw connections, so that all important housing parts are held together by the screw connections.According to the disclosure, the drive shaft arrangement has at least two drive shafts which are at least partially decoupled with respect to their operationally induced bending which results from the pressure medium loading of the working spaces. In this way, a bending of one drive shaft does not affect a bending of the other drive shaft.According to the disclosure, the two drive shafts are each rotatably mounted via two bearing points of the displacement unit assigned to them and thus substantially independently of one another.Preferably, the bearing points assigned to the respective drive shaft are arranged on different housing bases.In a particularly preferred development, the last drive mechanism and the central drive mechanism are connected in a rotationally fixed manner to one of the drive shafts and the latter is mounted via two bearing points. As already mentioned, the last drive unit is mounted in a floating manner outside the two bearing points, whereas the central drive unit is arranged between the two bearing points on the drive shaft.A development has proven to be advantageous if one of the two latter bearing points is arranged on the housing bottom of the central housing part and the other is arranged on the housing bottom of the last housing part.This drive shaft is particularly preferably supported in a floating manner and has two axial stops, in particular axial annular end surfaces, which can be brought into contact with parts of the displacement unit rotating in the same direction, in particular with the respective adjacently arranged engines, in order to limit an axial displacement of this drive shaft.According to the invention, one of the bearing points of both drive shafts is arranged on the housing base of the central housing part. The two drive shafts are then mounted with one of their end sections on the central housing base and with other of their end sections on the housing bases of the outer housing parts (first and last housing part).In a preferred development, the decoupling with respect to the operatively induced bending is realized in that the two drive shafts are connected in a flank-centered manner, in particular with a certain flank play. This is realized in particular via a spline shaft connection.Preferably, that one of the drive shafts to which the last, cantilevered drive mechanism is connected in a rotationally fixed manner, or to which the last drive mechanism and the central drive mechanism are connected in a rotationally fixed manner, has a larger outer diameter than another of the two drive shafts. In particular in a case in which the central and the last engine, or one of the two, are or is designed as an internal gear engine or ring gear engine or vane cell engine, it can thus be ensured that a deflection is greatly limited, which is advantageous for the safe operation of said engines or engine.In a preferred development, the first drive mechanism is connected to the other drive shaft in a rotationally fixed manner.An exemplary embodiment of a hydrostatic displacement unit according to the invention is explained in more detail below in five drawings. The following are shown: FIG. 1 shows an exemplary embodiment of a hydrostatic displacement unit in a perspective view from above, FIG. 2 shows the displacement unit in a perspective view from below, FIG. 3 shows a hydraulic circuit diagram of the displacement unit, FIG. 4 shows the displacement unit in a longitudinal section guided in alignment with a drive shaft axis, and FIG. 5 shows an exploded view of two of three hydraulic machines of the displacement unit.FIG. 1 shows a hydrostatic displacement unit 1 with a first hydraulic machine 2, a central hydraulic machine 4 and a last hydraulic machine 6. This housing 8 has a first housing part 10 for an engine of the first hydraulic machine 2, a central housing part 12 for an engine of the central hydraulic machine 4 and a last housing part 14 for an engine of the last hydraulic machine 6. The housing parts 10, 12, 14 and the housing cover 16 are arranged in series along an axis of rotation 18 of a drive shaft 20.The first hydraulic machine 2 is designed as an axial piston pump of swashplate construction with an adjustable stroke volume. The two hydraulic machines 4, 6 are each designed as a gerotor pump with a constant displacement volume. The displacement unit 1 serves, for example, for supplying pressure or pressure medium to a working hydraulic system, for example, for actuating hoisting units, slewing units or movable load arms of a mobile working machine, in particular a agricultural, forest or construction machine. Since hydraulic consumers of such working machines can have differential volumes, the first hydraulic machine 2 is provided for the open circuit. The two hydraulic machines 4, 6 are designed in such a way that they feed the hydraulic machine 2 and / or perform additional hydraulic functions of a mobile working machine, for example transmission lubrication, filtering and cooling of the fluid. Already mentioned working machines can have, for example, a continuously variable transmission (parallel path variable transmission), in which the hydrostatic displacement unit 1 is used for the control oil supply of the transmission shift or clutch actuation.The housing 8 has a plurality of pressure medium connections of the hydraulic machines 2, 4, 6. According to FIGS. 1 and 2, the housing cover 16 has both a suction connection 22 of the last hydraulic machine 6 and its pressure connection 24. Accordingly, no pressure medium connections are provided on the outside of the last housing part 14; instead, the pressure medium is supplied to the last hydraulic machine 6 via pressure medium channels formed in the housing cover 16. On the central housing part 12, in the same orientation as the pressure connection 24, a working connection (suction connection) A of the displacement unit 1 or of the first hydraulic machine 2 and a pressure connection 26 of the central hydraulic machine 4 are arranged. According to FIG. 2, a working connection B of the displacement unit 1 or of the first hydraulic machine 2, as well as a suction connection 28 of the second hydraulic machine 4, are provided on an underside of the central housing part 12. The suction connections 22 and 28 can be connected, for example, to a tank. Via the pressure connection 26, the central hydraulic machine 4 feeds pressure medium to the low-pressure side of the first hydraulic machine 2 at a predetermined charge pressure. The charge pressure is limited by a check valve 52 which is installed on the underside of the central housing part 12 according to FIG. 2. Alternatively, a pressure-reducing valve can also be used here for adjusting the pressure. The working pressure of the first hydraulic machine 2 can be adjusted by means of a pressure / delivery flow regulator 50 flange-mounted on the first housing part 10. The last hydraulic machine 6 is provided for additional hydrostatic functions of the displacement unit 1 and thus, for example, of the mobile working machine (not shown).As indicated in FIG. 1 and as can be clearly seen in FIG. 2, the housing parts 10, 12, 14 and the housing cover 16 are screwed together by means of four long screws 32. These pass through the housing cover 16, the last housing part 14 and the central housing part 12 and are screwed into blind holes (not shown) of the first housing part 10 which are designed with an internal thread.FIG. 3 shows a hydraulic circuit diagram of the displacement unit 1, supplemented by a tank T. It can be seen that the three hydraulic machines 2, 4, 6 each have an engine 34, 36, 38. The engines 36, 38 are connected to a drive shaft 40 and the engine 34 to the drive shaft 20 in a rotationally fixed manner. The drive shafts 20, 40 are connected in a rotationally fixed manner via a spline shaft connection 42 and thus form a drive shaft arrangement. In addition to the already described pressure medium connections 22, 24, 26, 28 and the working connections A, B, FIG. 3 shows a leakage connection 44, which is arranged on an end face of the first housing part 10 according to FIG. 1. This collects the leakage of all engines 34, 36, 38 toward the tank T. Furthermore, a swivel cradle 46 of the first hydraulic machine 2 is schematically shown, which is linked by its hydraulic actuating cylinder 48. Its pressure chamber is connected fluidically to a pump regulator 50, via which a displacement volume of the first hydraulic machine 2 can be adjusted as a function of the load pressure present at the working connection B. A more detailed description of the first hydraulic machine 2 can be omitted at this point, since its mode of operation is part of the relevant prior art. A pressure side of the central hydraulic machine 4 can be fluidically connected to the tank T via a spring-biased nonreturn valve 52, which is set at 14 bar, and is thus protected against exceeding 14 bar.FIG. 4 shows the displacement unit 1 according to the preceding figures in a longitudinal section A-A taken through the axis of rotation 18, as defined in FIG. 2. It can be clearly seen that the housing parts 10, 12, 14 are each pot-shaped, each individual housing having a housing base 54, 56, 58, respectively. Each housing part 10, 12, 14 also has a housing opening 60, 62, 64, respectively. In this case, the first power unit 34 of the first hydraulic machine 2 is arranged in the first housing part 10. This has a cylinder drum 68 with a plurality of cylinder bores 70, in each of which a working piston 72 is accommodated in an axially displaceable manner. The working pistons 72 are slidably supported via sliding shoes on a sliding surface of the swivel cradle 46. Its pivot angle is adjustable for adjusting the displacement volume via the adjusting cylinder 48. A spring 74 acts as a reset element. A precisely manufactured, circular cylindrical receiving space 76 is formed in the central housing part 12, in which receiving space the central power unit 36 of the central hydraulic machine 4 designed as a gerotor pump. Similarly, in the last housing part 14, the last drive unit 38 of the last hydraulic machine 6, which is designed as a gerotor pump, is arranged in a circular cylindrical receiving space 80.It can be clearly seen that the last drive unit 38 is mounted in a floating manner on an end section of the drive shaft 40. The latter drive shaft 40 is supported in a floating manner on the housing base 56 via a rolling bearing 84 and on the housing base 58 via a rolling bearing 86. Consequently, pinions of the two hydraulic machines 4, 6, which are connected to the drive shaft 40 in a rotationally fixed manner, are also mounted in a floating manner thereon. An axial displacement of the drive shaft 40 is limited by axial stops 87 and 88, which are designed as annular end faces on the drive shaft 40. The stop 87 can strike against the pinion 90, which rotates with the drive shaft 40, and the stop 88 can strike against an inner ring of a rolling bearing 92, which runs with the drive shaft 20 and is received in sections in the housing base 56. The drive shaft 20 is rotatably mounted on the housing base 54 via a further rolling bearing 94. The drive shafts 20, 40 are connected via the flank-centered spline shaft connection 42, wherein an end section of the drive shaft 20 is immersed in an end section of the drive shaft 40 designed as a hollow shaft. Due to the larger diameter, the drive shaft 40 has good bending stiffness, which opposes an operating behavior of the two hydraulic machines 4, 6 designed as gerotor pumps. A displacement volume of the central hydraulic machine 4 is greater than a maximum displacement volume of the first hydraulic machine 2, whereby an undersupply of the latter is avoided. A displacement volume of the last hydraulic machine 6 is larger than that of the central hydraulic machine 4.FIG. 5 shows an exploded view of parts of the central hydraulic machine 4 and of the last hydraulic machine 6, and of the housing cover 16; it is possible to see in this view through-bores 96, 98, 100, which penetrate through the central housing part 12 or the last housing part 14 and the housing cover 16, and which are penetrated by the screws 32. End portions of the screws 32 are screwed into the pot-shaped housing part 10 of the first hydraulic machine 2 in the assembled state. Also clearly seen are an internal gear ring 102 engageable with pinion 90 to form the last power unit 82, and a pinion 104 of the central power unit 36.In contrast to the illustration, at least one of the two hydraulic machines 4, 6 can be designed as a constant vane pump or as a vane pump with an adjustable displacement volume.A hydrostatic displacement unit with at least three hydraulic machines is disclosed, wherein an engine of one of the hydraulic machines is mounted in a cantilevered manner.List of reference characters1 Hydrostatic displacement unit 2 First hydraulic machine 4 Central hydraulic machine 6 Last hydraulic machine 8 Housing 10 First housing part 12 Central housing part 14 Last housing part 16 Housing cover 18 Axis of rotation 20 Drive shaft 22, 28 Suction connection 24, 26 Pressure connection 32 Screw 34 First drive unit 36 Central drive unit 38 Last drive unit 40 Drive shaft 42 Spline shaft connection 44 Leakage connection 46 Swashplate 48 Adjusting cylinder 50 Pump regulator 52 Nonreturn valve 54, 56, 58 Housing base 60, 62, 64 Housing opening 68 Cylinder drum 70 Cylinder bore 72 Working piston 74 Spring 76 Receiving space 80 Receiving space 84, 86 Rolling bearing 87, 88 Stop 90 Pinion 92, 94 Rolling bearing 96, 98, 100 Passage recess 102 Inner toothed ring 104 Pinion A, B Working connection

Claims

Hydrostatic displacement unit (1) having at least three hydrostatic power engines (34, 36, 38) which are arranged in a rotationally fixed connection to a power shaft arrangement (20, 40) and along the latter in series, and which each have at least one hydrostatic working space which can be fluidically connected alternately to a high-pressure space (24, 26, B) and to a low-pressure space (22, 28, A) of the displacement unit (1), wherein one of the last ones (38) of the power engines (34, 36, 38) in the series is mounted in a cantilevered manner, wherein the power shaft arrangement (20, 40) has at least two power shafts (20, 40) which are at least partially decoupled with respect to their operatively induced bending, and which are each mounted rotatably via two bearing points (84, 86, 92, 94) and substantially independently of one another, and having a housing (8) having three pot-shaped housing parts (10, 12, 14) which each have a housing base (54, 56, 56, 14), 58) and a housing opening (60, 62, 64) arranged substantially opposite the housing base (54, 56, 58), wherein the last drive mechanism (38) is accommodated at least in sections or completely in an interior of a last (14) of the housing parts (10, 12, 14) in the row and a central (36) of the drive mechanisms (34, 36, 38) is accommodated in an interior of a central (12) of the housing parts (10, 12, 14) in the row and a first (34) of the drive mechanisms (34, 36, 38) is accommodated at least in sections or completely in an interior of a first (10) of the housing parts (10, 12, 14) in the row, characterized in that one (84, 92) each of the bearing points (84, 86, 92, 94) of both drive shafts (20, 40) is arranged on the housing base (56) of the central housing part (12).Displacer unit (1) according to claim 1, wherein the last (38) of the engines (34, 36, 38) and / or the central (36) of the engines (34, 36, 38) is each that of an internal gear machine or a ring gear machine (4, 6) or a vane cell machine of the displacer unit (1), and wherein an in-line first (34) of the engines (34, 36, 38) is that of an axial piston machine (2) of the displacer unit (1).Displacement unit (1) according to claim 1 or 2, wherein the housing opening (62) of the central housing part (12) is closed at least in sections via the housing base (58) of the last housing part (14) and the housing opening (60) of the first housing part (10) is closed via the housing base (56) of the central housing part (12).Displacement unit (1) according to one of Claims 1 to 3, wherein the three housing parts (10, 12, 14) are connected via a plurality of screws (32) which pass through at least the last housing part (14) and the central housing part (12).Displacement unit (1) according to one of the preceding claims, wherein the two drive shafts (20, 40) are connected in a flank-centered manner.Displacement unit (1) according to one of the preceding claims, wherein one (40) of the two drive shafts (20, 40), to which the last drive shaft is connected in a rotationally fixed manner, or to which the last drive shaft (38) and the central drive shaft (36) are connected in a rotationally fixed manner, has a larger diameter than another (40) of the two drive shafts (20, 40).

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