Hydrostatic displacement engine

Abstract

A hydrostatic displacement machine is disclosed, which is designed with an adjustable displacement volume, comprising a first assembly (86) with a hydrostatic adjustment device (32) which is coupled to an actuator (28) whose position determines the displacement volume, wherein the adjustment device (32) has an actuating cylinder (34) which can be actuated with actuating pressure medium by a control valve of the displacement machine according to a displacement volume setpoint, and the actuating piston (38) is guided axially displaceably therein along its central axis (50), characterized in that the displacement machine (1) has a second assembly (88) modularly mounted on the first assembly (86), which is operatively connected to the actuating piston (38) so that an actuating position of the actuating piston (38), in particular a pivot angle or position position, can be detected and / or determined via it.

Description

The invention relates to a hydrostatic displacement machine according to claim 1, such as an axial piston machine, for example of swashplate construction. This is a hydrostatic displacement machine which is designed with an adjustable displacement volume, having a first assembly with a hydrostatic adjustment device which is coupled to an actuating element, from whose setting position the displacement volume is dependent, wherein the adjustment device has an adjusting cylinder which can be acted upon by a setting valve of the displacement machine according to a displacement volume setpoint value with setting pressure medium and has a setting piston which is guided therein so as to be axially displaceable along its central axis.A hydrostatic displacement machine of the generic type is designed with an adjustable displacement volume and has a hydrostatic adjustment device with a cylinder, in particular an adjusting cylinder, and an adjusting piston guided therein. The adjusting piston directs an adjusting element or adjusting element of the displacement machine, on the adjusting position of which the displacement or stroke volume of the displacement machine depends.The publication DE 10 2017 213 457 A1 shows such a displacement machine in a concrete embodiment as an axial piston machine of swashplate construction, wherein the actuator is a swivel cradle on which the swashplate is arranged. The setting position of the swivel cradle, i.e. its swivel angle, results in the stroke of the working pistons slidingly supported thereon, whereby the displacement volume is again defined.In many hydrostatic applications, such as a traction drive or a working hydraulic system, for example, when the displacement volume is to be controlled or regulated, it is important to know the exact position of the actuator or of the adjusting device. Knowing this, it is possible to infer the actual displacement volume. For this purpose, according to the prior art, for example, a position sensor can be used, which is designed, for example, as a pivot angle sensor for detecting the pivot angle of the pivoting cradle or as a position sensor for detecting an adjustment path. Such hardware implementations with sensors are cost-intensive and therefore are not always available in practical implementation for cost reasons.Alternatively, software-based solutions are known from the prior art, which are so-called "estimators" for the pivot angle or the position. The pivot angle, or the adjustment position, is estimated by means of an algorithm. However, for accurate regulation, the estimation has on the one hand too great a deviation, and on the other hand, in preparation for the estimator, high expenses are required for determining required characteristic maps of the hydrostatic units, for example by simulation and / or experiment. In addition, the transferability of the results obtained in this way is restricted on account of changing operating conditions, such as temperature, viscosity, dynamic behavior, tolerances, scattering, air in oil, rotational speed, pressure and the like.In contrast, the object of the invention is to provide a hydrostatic displacement machine whose displacement volume can be detected or determined with little effort.The object is achieved by a hydrostatic displacement machine having the features of claim 1, that is to say in that the displacement machine has a second assembly which is mounted on the first assembly in a modular manner and is operatively connected to the actuating piston, with the result that an actuating position of the actuating piston, in particular a pivot angle or position position, can be detected and / or determined via said second assembly.Advantageous further developments of the invention are described in the respective dependent claims.A hydrostatic displacement machine is designed with an adjustable displacement volume and has a first assembly with a housing and a hydrostatic adjustment device which is coupled to an actuator, the displacement volume being dependent on its setting position. The adjusting device has an adjusting cylinder with a first adjusting cylinder section designed as a screw-in sleeve, in particular screwed into the housing, and a second adjusting cylinder section formed by the housing, wherein an adjusting piston, which can be acted upon by adjusting pressure medium by an adjusting valve of the displacement machine as a function of a displacement volume setpoint value, is guided axially displaceably along its central axis on the two adjusting cylinder sections. According to the invention, the displacement machine has a second assembly mounted on the first assembly as a module, which is operatively connected to the actuating piston, so that an actuating position of the actuating piston, in particular a pivot angle or position position, can be detected and / or determined via it.In this way, a simple determination of the pivot angle and / or position in terms of the device is created in hydrostatic pumps, motors or gear mechanisms without additional sensor systems.In addition, for example, the actuating position of a shift element, for example a clutch, a synchronizer, or a claw clutch, the actuating position of a shift element with respect to 2WD and 4WD of a wheel drive, the actuating position of a steering system, a brake valve, or a parking brake can be easily detected or determined.Areas of application of the displacement unit according to the invention are in particular construction machines, agricultural machines, mining, ship travel and generally hydrostatic drives.According to a further development, the hydrostatic adjusting device is configured in a modular manner, in particular in a cartridge or cartridge construction, which simplifies its assembly and disassembly even further.Preferably, the control valve is a component of the modular, second assembly.According to a preferred embodiment, the displacement machine is designed as an axial piston machine of swashplate construction and the actuator is a swivel cradle having the swashplate. Alternatively, the displacement machine is designed as an axial piston machine of the oblique axis type and the actuator is a pivot axis.The displacement unit advantageously has a control unit, by means of which the displacement volume can be regulated as a function of the detected and / or determined actuating position.According to the invention, this provides automatic compensation of flow forces at the control valve, in particular at its control edges.In addition, automatic compensation of restoring forces acting on the adjusting device is provided, so that the ascertainment of a characteristic diagram can be omitted.In addition, there is automatic compensation of tolerances and a scatter of hydrostatic units.In sum, the simple and process-safe detection and / or determination of the adjustment position and thus of the displacement volume according to the invention allows simple regulation and / or control of the hydrostatic displacement machine, which leads to an increase in a control and / or regulation quality and a machine performance.Due to the second assembly according to the invention, a cost reduction is achieved by saving sensor technology (pivot angle sensor, position sensor, switch) for determining the actuating position.A further advantage results for the electronic regulation of a pressure cut-off. Here too, there is an improvement in the performance.According to a preferred embodiment, the operative connection of the second assembly to the actuating pistons is realized by at least one inductive unit, wherein said unit has components which are arranged distributed over the assemblies and are in inductive operative connection and via which the actuating position can be detected, in particular via the relative position thereof with respect to one another.According to a preferred development, a boundary or boundary surface between the assemblies is determined by a functional gap, in particular an air gap, between these components of the two assemblies.For the purpose of modular connection of the two modules, the components can be assembled or put together by means of the simple fastening of the second module to the first module, or vice versa, to form the inductive unit, in particular an operable inductive unit.An exemplary embodiment of a displacement machine according to the invention is illustrated in the drawings. The invention will now be explained with reference to the figures of these drawings.The following are shown: FIG. 1 shows an exemplary embodiment of a hydrostatic displacement machine in a longitudinal section, and FIG. 2 shows the displacement machine according to FIG. 1 in a longitudinal section, from above.FIG. 1 shows a displacement machine 1 designed as an axial piston machine with an adjustable displacement volume in swashplate construction; FIG. 1 shows a first assembly 86 of the displacement machine 1; the first assembly 86 comprises a housing 2 with a substantially pot-shaped housing part 4 and a housing cover 6 having working connections (not shown); a drive shaft 8 is rotatably mounted in the housing 2. For transmitting a torque, the drive shaft 8 has a shaft stub 12 which passes through a base 10 of the housing part 4. The drive shaft 8 has an external toothing 14 in a central region, via which it is connected to a cylinder drum 16 in a rotationally fixed manner. This has a plurality of cylinder bores 19 which are arranged on a pitch circle running concentrically with respect to an axis of rotation 18 of the drive shaft and cylinder drum 16 and in each of which a working piston 20 is accommodated in an axially displaceable manner. A pair of working piston 20 and cylinder bore 19 each defines a hydrostatic working chamber 22 which, via a control disk 24 traversed by through-recesses, comes into alternating pressure medium connection with the working connections during rotation of the cylinder drum 16.At an end face of the cylinder drum 16 remote from the control disk 24, the working pistons 20 emerge from the cylinder drum 16 and are supported in a sliding manner via their piston heads accommodated in sliding shoes on an swashplate 26 whose pivot angle is adjustable with respect to the axis of rotation 18. The latter is designed as a sliding surface of a swivel cradle 28 mounted pivotably in the housing part 4. This is coupled to a hydrostatic adjusting device 32 via a pin 30 formed integrally with the swivel cradle and a sliding block 31 rotatably mounted thereon. This operates hydrostatically, that is to say it consists essentially of a hydraulic cylinder and a double-acting actuating piston 38 which is effectively acted upon by actuating pressure medium in both directions. The actuating pressure medium is provided by an external actuating pressure medium source. A more detailed description of the adjusting device 32, its interaction with the pivoting cradle and its, in particular inner, structure, is given with reference to the following figures.FIG. 2 shows the axial piston machine 1 in a cross section B-B which, according to FIG. 1, is guided at the height of a central axis 50 of the adjusting piston 38 parallel to the axis of rotation 18. In this view, in addition to the first assembly 86 described above, a second assembly 88 can be seen, which is fastened to the first assembly 86 in a modular manner.According to FIG. 2, the adjusting piston 38 is of double-acting design. This means that it has on each side of a groove 44 a piston surface 52, 54 each of which can be acted upon by adjusting pressure means. The adjusting piston 38 has a first piston surface 52 which delimits a first cavity 56 formed in the adjusting piston 38 on this side of the groove 44 as a pressure-effective surface. Furthermore, the adjusting piston 38 has beyond the groove 44 a second piston surface 54 counteracting the first piston surface 52, which is also predominantly designed as an end surface of a cavity 58 of the adjusting piston 38. On this side and beyond the groove 44, the adjusting piston 38 is thus formed hollow. This saves weight on the one hand and allows the arrangement of springs 60, 62 in the first cavity 56 on the other hand, these springs being provided for centering and prestressing the adjusting piston 38 in a central position or zero position. In the illustrated embodiment, these are a small-radius spring 60 and another spring 62 concentrically surrounding the same.The hydrostatic adjusting device 32 is designed at least in sections in a cartridge or cartridge construction. In the exemplary embodiment shown, this is implemented by means of a first adjusting cylinder section 34 designed as a screw-in sleeve. The adjusting piston 38 is thus received on this side of the groove 44 with its first portion, in which the first cavity 56 is formed, not directly in the housing part 4, but rather in the screw-in sleeve 34 so as to be guided in an axially displaceable manner. With its second end section, the adjusting piston 38 is accommodated in a second adjusting cylinder section 64 of the housing part 4 and guided in an axially displaceable manner, wherein the inner lateral surface of the second adjusting cylinder section 64, on which it is guided, is manufactured efficiently by turning in the exemplary embodiment.By using the cartridge construction, only the one running surface of the second adjusting cylinder section 64 has to be provided on the housing part 4 for forming the adjusting cylinder 34, 64, instead of two, manufactured precisely.The screw-in sleeve 34 is substantially pot-shaped, wherein the first end section of the adjusting piston 38 dips into the pot opening.A bottom 66 of the screw-in sleeve 34 closes off the screw-in sleeve 34 from the outside.Fixed to the cylinder, and thus fixed to the housing, is an adjusting rod or rod 68 secured centrally to the bottom 66 via a secured screw connection 70. This passes through the first cavity 56 as far as its bottom section and partially protrudes into a second cavity 72 opening into the first cavity 56. The second cavity 72 represents a necessary free space or immersion space for the rod 68 upon movement of the adjusting piston 38 downward in FIG. 2.At an end portion in the region of the second cavity 72, the rod 68 has a radially widened, plunger-shaped, cylinder-fixed stop 74; another, cylinder-fixed stop 76 in the form of a secured nut is screwed and fixed on the rod 68 between the base 66 and the last-mentioned stop 74. The springs 60, 62 are clamped between the stops 74, 76 by means of spring plates 78, 80 which are each embodied in multiple parts in the exemplary embodiment. The two stops 74, 76 mentioned are fixed to the cylinder and can be adjusted.In addition, the adjusting device 32 has two piston-fixed stops 82, 84 which are selected in their distance D and are matched to the springs 60, 62 in such a way that the adjusting piston 38 and thus the pivoting cradle 28 according to FIG. 1 is prestressed with a specific prestressing force into the neutral or zero position in which the working pistons do not execute a working stroke when the drive shaft 8 rotates. A sleeve 86 is guided axially displaceably on the rod 68, by means of which sleeve a stroke of the respective spring plate 78, 80 toward the other spring plate 80, 78 is limited.At both end sections of the adjusting piston 38, both in the second adjusting cylinder section 64 and in the first adjusting cylinder section / the screw-in sleeve 34, the adjusting piston 38 is radially supported via a radially flat sleeve-shaped and one-piece sleeve arranged on the outer circumferential surface of the adjusting piston 38 in a toothed groove. This consists of tough and slidable PTFE, so that both the guidance of the adjusting piston 38 in the second adjusting cylinder section 64 and the screw-in sleeve 34 and the fluidic sealing of the two cylinder spaces of the adjusting device 32 that can be acted upon by adjusting pressure medium are ensured via these.The second assembly 88 forms a measuring unit for indirectly detecting the pivot angle of the swashplate 26, which measurement unit inductively detects the actuating position of the actuating piston 38, which can be seen in particular with reference to FIG. 2.The second assembly 88 has a housing 100 in / on which a control coil 90 of a control valve 91, the control valve 91, a CAN connection 92, an inductive control position pickup 94, an integrated circuit board 96 and, in sections, an inductive control position pickup 98 are accommodated / arranged.The inductive setting position transducer 98 is motion-coupled to the setting piston 38. The setting position of the setting piston 38 is dependent on the pivot angle position / the pivot angle of the swashplate 26 and thus on the displacement volume.The inductive setting position pickup 94 records the setting position and transmits it via a CAN connection 92 to a control unit (not shown) of the displacement machine 1. For this purpose, the control unit balances a displacement volume setpoint value with the actual displacement volume value determined from the detected actuating position and controls the control coil 90 of the actuating valve 91 according to the determined control deviation, so that the actuating piston 38 is accordingly acted upon by actuating pressure medium or is relieved therefrom.List of reference numbers:1 Hydrostatic axial piston machine 2 Housing 4 Pot-shaped housing part 6 Housing cover 8 Drive shaft 10 Base 12 Shaft stump 14 External toothing 16 Cylinder drum 18 Axis of rotation 19 Cylinder bore 20 Working piston 22 Hydrostatic working chamber 24 Control disk 26 Swashplate 27 Through-recess 28 Actuator / swivel cradle 29 Bearing surface 30 Journal 31 Sliding block 32 Hydrostatic adjusting device 34 First adjusting cylinder section / screw-in sleeve 38 Adjusting piston 40 Side surface 42 Axis of rotation 44 Recess 46 Base 48 Flank 50 Central axis 52, 54 Piston surface 56 First cavity 58 Cavity 60, 62 Spring 64 Second adjusting cylinder section 66 Base 68 Rod 70 Screw connection 72 Second cavity 74, 76 Cylinder-fixed stop 78, 80 Spring plate 82, 84 bulb-fixed stop 86 first assembly 88 second assembly / measuring unit 90 control coil control valve 91 control valve 92 connection CAN 94 control position sensor 96 printed circuit board PCB 98 control position sensor 100 housing second assemblyReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedDE 10 2017 213 457 A1

[0003]

Claims

Hydrostatic displacement machine which is designed with an adjustable displacement volume, having a first assembly (86) with a housing (2) and a hydrostatic adjustment device (32) which is coupled to an actuating element (28), the displacement volume being dependent on the setting position of which actuating element the displacement volume is dependent, wherein the adjustment device (32) has an actuating cylinder (34, 64) with a first actuating cylinder section (34) designed as a screw-in sleeve and a second actuating cylinder section (64) formed by the housing (2), wherein an actuating piston (38) which can be acted upon by actuating pressure medium by an actuating valve of the displacement machine (1) according to a displacement volume setpoint value is guided in the two actuating cylinder sections (34, 64) in an axially displaceable manner along its central axis (50), characterized in that the displacement machine (1) has a second assembly (88) which is mounted in a modular manner on the first assembly (86), which is operatively connected to the actuating piston (38), so that an actuating position of the actuating piston (38), in particular a pivot angle or position, can be detected and / or determined via the second assembly (88).Displacement machine according to claim 1, wherein the hydrostatic adjusting device (32) is designed at least in sections in a cartridge or cartridge construction.Displacement machine according to Claim 1 or 2, wherein the displacement machine (1) is designed as an axial piston machine of swashplate construction and the actuator is designed as a pivoting cradle (28) having the swashplate (26), or wherein the displacement machine is designed as an axial piston machine of swashplate construction and the actuator is designed as a pivot axis.Displacement machine according to one of the preceding claims, having a control unit by means of which the displacement volume can be regulated as a function of the detected and / or determined actuating position.Displacement machine according to one of the preceding claims, having at least one inductive unit with components (94, 98) which are arranged distributed over the first assembly (86) and the second assembly (88) and via the relative position of which the setting position can be detected.Displacement machine according to one of the preceding claims, wherein a boundary or boundary surface between the first assembly (86) and the second assembly (88) is determined by a functional gap, in particular an air gap, between the components (94, 98).Displacement machine according to claim 5 or 6, wherein the components (94, 98) are assembled or can be assembled to form the, in particular functional, inductive unit by fastening the second assembly (88) to the first assembly (86) or vice versa.

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