Hydraulic, stroke-adjustable piston machine

Abstract

The invention relates to a hydraulic, stroke-adjustable piston machine (1) comprising: a drive shaft (10) having an annular sliding body (11) which, on its inner side, has a plurality of polygonally arranged sliding surfaces (12); a plurality of pistons (32) which are each supported on one of the sliding surfaces (12); a control body (20) which has a control pin (21) on or with which the cylinder body (30) can rotate about the control pin axis (7); wherein the piston machine (1) is designed in such a way that the pistons (32) and, with said pistons, the cylinder block (30) are rotated by the sliding body (11) during rotation of the drive shaft (10), and wherein the control body (20) is linearly displaceable along a control line (8) such that the control pin (21) can be adjusted eccentrically relative to the shaft (10) so that, during rotation of the drive shaft (10) about the shaft axis (6) and rotation of the cylinder block (30) about the pin axis (7), the working space in the cylinder (31) cyclically increases and decreases, wherein the sliding body (11) is designed as a polygonal cone having a cone angle α which indicates the orientation of the sliding surfaces (12) relative to the shaft axis (6), and the control line (8) is arranged at a control angle β to the pin axis (7), and wherein both the cone angle α and the control angle β are within the range of 15° to 80°; and wherein the cone angle α and the control angle β differ by a maximum of 3°.

Description

[0001] Hydraulic, stroke-adjustable piston machine

[0002] The invention relates to a hydraulic, stroke-adjustable piston machine comprising a housing, a drive shaft rotatably mounted therein with an annular sliding body which has a plurality of polygonally arranged sliding surfaces on its inside, as well as a plurality of pistons which are each supported on one of the sliding surfaces, and an associated cylinder for each piston in which the respective piston can move back and forth, wherein the cylinders together form a cylinder block, and wherein a fluid-filled working chamber delimited by the piston is formed in each cylinder, further comprising a control body which has a control pin on or with which the cylinder block can rotate about the control pin axis.The piston engine is designed in such a way that the pistons, and with them the cylinder block, are rotated by the sliding body when the drive shaft rotates. The control body can be moved linearly along a control line such that the control pin can be adjusted eccentrically to the shaft. As the drive shaft rotates around the shaft axis and the cylinder block rotates around the pin axis, the working space in the cylinder cyclically increases and decreases. The respective cylinders are cyclically connected, one after the other, to a first fluid opening and another fluid opening via a cylinder opening. This allows the stroke of the piston engine to be precisely adjusted.

[0003] In particular, a piston machine is designed so that it can operate as a piston pump or as a piston motor. The cyclically increasing and decreasing working space in the cylinders either creates a pumping effect on the fluid between the first and the further fluid opening due to the rotation of the drive shaft. Or a motor effect is generated, i.e., a rotation of the drive shaft is generated due to a pressure difference of the fluid between the first and the further fluid opening. The size of the eccentricity e of the control pin to the shaft axis determines the size of the volume change of the working spaces during rotation of the cylinder body, which rotates eccentrically to the housing. At the bottom dead center (BDC) of the piston, the working space is at its minimum, and at the top dead center (TDC) of the piston, the working space is at its maximum – relative to one revolution. The eccentricity e thus determines the pumping volume of the pump or the displacement of the engine.At maximum eccentricity e, the machine operates at its maximum stroke. At reduced eccentricity e, it operates in partial stroke mode. And at eccentricity e=0, it operates in zero stroke mode.

[0004] Piston pumps are used, for example, in hydraulically controlled movements to supply the hydraulic pistons with fluid at the desired pressure for this movement.

[0005] Piston pumps designed as radial piston pumps are known in the prior art, for example, from DE 102011053148 A1 and WO 2022 / 013062 A1. The designs presented here feature a rotating eccentric that cyclically moves the pistons arranged radially in the housing back and forth, thus creating a pumping effect on the fluid. These radial piston pumps are externally pressurized, since the working chamber in the cylinder is located radially outside the pistons.

[0006] Further designs are known from WO 96 / 32589 A1. This shows an internally pressurized radial piston pump. The working chamber in the cylinder is located radially within the pistons. Furthermore, the rotor rotates with the cylinders in an eccentrically arranged cam ring. The pistons slide on the circular inner surface of the cam ring. A joint is provided between the piston and the sliding block to enable the necessary pendulum movement. A further development of this radial piston pump is described in WO 2020 / 254501 A1. To avoid the joint and to save installation space, spherical piston heads are proposed, which allow the pendulum movement in the cylinder.

[0007] Variable-stroke axial piston pumps, in which the piston's longitudinal axis is essentially parallel to the shaft axis, are also known in the prior art. These designs have the disadvantage of significant efficiency losses due to internal friction and, due to their massive design, require a lot of space.

[0008] The object of the invention is now to further develop and improve the piston engine so that it becomes more compact and has fewer losses and thus a higher efficiency.

[0009] The object is achieved by a piston engine according to claim 1. Further advantageous features are mentioned in the dependent claims.

[0010] According to the invention, the hydraulic piston machine is characterized in that the sliding body is designed as a polygonal cone with a cone angle α, which indicates the alignment of the sliding surfaces to the shaft axis, and in that the control line is arranged at a control angle β to the journal axis, wherein the cone angle α and the control angle β both lie in the range between 15° and 80°, preferably between 30° and 60°, and wherein the cone angle α and the control angle β have a maximum difference of 3°.

[0011] A polygonal cone means that the sliding body is arranged conically on the drive shaft, and the sliding surfaces are arranged in a polygonal shape on the inside of the cone. The alignment of the sliding surfaces is parallel to the cone angle α. This results in the pistons, which are supported perpendicularly on the sliding surfaces, being positioned with their longitudinal axis L at an angle to the shaft axis. Instead of a radial piston pump or an axial piston pump, as is known, the design according to the invention is now a diagonal piston pump.

[0012] The cylinder block has a conical inner surface that rests on a similarly conical control piston sliding surface of the control body. As the cylinder block rotates, it slides over the control piston sliding surface. The drive shaft is preferably mounted in the housing via rolling bearings, such as ball bearings. The bearings in the housing ensure precise positioning of the drive shaft.

[0013] The linear displacement of the control body occurs along the control line, which forms the control angle ß with the shaft axis. It is important that the shaft axis and the control pin with its pin axis are arranged essentially parallel to each other. A deviation of up to + / -3° can be considered essentially parallel. This condition is met when the cone angle α and the control angle ß differ by a maximum of 3°. The distance between the shaft axis and the pin axis indicates the eccentricity e.

[0014] The aforementioned slight deviation of up to 3° can be deliberately designed to achieve a slightly variable contact line between the piston circumference and the cylinder inner wall. This reduces local wear.

[0015] The advantage of this inventive design is that, due to the angled arrangement of the pistons and the control line, the adjustment of the control pin, i.e. the eccentricity e, only affects bottom dead center BDC, at which the working space in rotation is at its maximum, and has little or no effect on top dead center TDC, at which the working space in rotation is at its minimum. If the cone angle α and control angle β are the same, the control line is parallel to the longitudinal axis L of the cylinder at bottom dead center BDC and perpendicular to the longitudinal axis L of the cylinder at top dead center TDC. As a result, the dead volume remaining in the cylinder at top dead center TDC remains constant and is therefore independent of the eccentricity setting. The reciprocating piston engine according to the invention can therefore be operated very efficiently with a constantly low dead volume in the cylinder, even in partial stroke operation, in which the maximum working space volume is not used.

[0016] In radial or axial piston machines, however, the piston moves during partial stroke operation in such a way that the dead volume remaining in the cylinder increases the shorter the stroke. This makes these machines increasingly inefficient during partial stroke operation. A further advantage of the design according to the invention is that there is no pendulum movement between the piston and cylinder, and therefore no transverse forces between the piston and cylinder. No pistons, connecting rods, or similar components are required. The pistons move purely linearly within the cylinder. Piston and cylinder are coaxial with each other in every state of motion. The piston slides back and forth with its contact surface on the corresponding sliding surface of the sliding body. The longitudinal axis L of the piston is always exactly perpendicular to the sliding surface of the sliding body.

[0017] This leads to a significant overall increase in efficiency, and internal losses are significantly reduced. Furthermore, the piston strokes in the cylinder are precisely sinusoidal, which is not possible with previously known radial piston machines. This improves concentricity and reduces imbalance forces and associated losses. Above all, friction and local wear are reduced. Furthermore, the cylinders can be designed with thinner walls if necessary due to the elimination of transverse forces, which saves space and weight for the rotating parts.

[0018] Furthermore, there are no radial forces from the pistons to the cylinders caused by the kinematics of the linear adjustment of the control body.

[0019] In addition, the design according to the invention is very compact and, thanks to the inclined sliding surfaces, can be manufactured and assembled much more easily and cost-effectively. Another advantage is that the diagonal piston machine is less sensitive to thermal shocks, i.e., when fluids with very different temperatures are supplied. The inclined conical surfaces between which the pistons and cylinders are arranged hydrostatically compensate for different expansions of the parts via the working spaces and the fluid.

[0020] In radial piston pumps, however, thermal shock poses a risk that gap dimensions will become too small, causing the radial piston pump to jam and be damaged. Preferably, the cone angle α and the control angle β are both in the range between 40° and 50°, and especially 45°. And particularly preferably, the cone angle α and the control angle β differ by less than 5°, and most preferably, they are the same. This allows the influence of adjusting the eccentricity e to be further limited to the height h of the working chamber at bottom dead center (BDC) without affecting the conditions at top dead center (TDC). This allows the advantages to be utilized even more effectively.

[0021] Furthermore, the radial piston machine can be designed in such a way that it can operate both as a radial piston pump and as a radial piston motor, and in particular can operate in the so-called four-quadrant operation, i.e. that it can drive the drive shaft in both directions of rotation, and that the pumping action can take place both from the first fluid opening to the further fluid opening and in the opposite direction.

[0022] Thanks to four-quadrant operation, the radial piston machine can be used very efficiently to recover energy from a rotary motion with simultaneous braking effect. This energy is used to increase the pressure of the fluid and thus store it. This allows construction machinery with hydraulic drives, for example, to operate much more energy-efficiently.

[0023] During pumping operation, the drive shaft is driven, causing the sliding body to rotate. The sliding body forces the pistons to rotate, which in turn creates a reciprocating movement in the cylinder. This causes the cylinder body to rotate and the working chambers to cyclically increase and decrease in size. The pistons slide back and forth laterally on the sliding surfaces of the sliding body. The working chambers in the cylinder are cyclically connected to the first fluid opening and the other fluid opening, creating a pressure difference and thus a pumping effect on the fluid. During engine operation, the pressure difference of the fluid between the first and the other fluid opening causes the working chambers to increase on the high-pressure side and decrease on the low-pressure side. The odd number of pistons causes the cylinder block to rotate on the control body, resulting in a cyclical change in the working chambers.The rotation of the cylinder block and the pistons also drives the sliding body, which is connected to the drive shaft.

[0024] Particularly preferably, the piston engine has an odd number of pistons. This prevents one of the cylinders from passing through top dead center (TDC) and bottom dead center (BDC) simultaneously. This reduces pressure pulsations or torque pulsations. Furthermore, it prevents a blocking position in which the same number of working chambers are connected to the low-pressure side as to the high-pressure side of the fluid supply.

[0025] A particularly powerful and at the same time compact design is achieved if the cylinders have a circular cross-section and the diameter of the cylinders (32) is between 3 mm and 100 mm, preferably between 10 mm and 50 mm.

[0026] It is particularly advantageous for the linear adjustment of the control body to include a hydraulic control, such as a hydraulic control piston. This allows the crank pin to be adjusted easily and reliably. In particular, a bushing for linear guidance can be provided, which interacts with the control body.

[0027] In particular, an additional housing may be provided, which is connected to the housing and in which the control body is guided, particularly in a bushing. The additional housing thus ensures the precise positioning of the control body relative to the shaft axis. The control body can preferably have a rectangular area, thus ensuring even more precise guidance in the additional housing of the piston engine.

[0028] In a further preferred embodiment, the maximum displacement of the control body along the control line is at least 3 mm and a maximum of 100 mm. This provides sufficient adjustment for the eccentricity e while still allowing for a very compact design.

[0029] Furthermore, it is advantageous if the control body has a first fluid channel on the inside, which is connected to the first fluid opening, and a further fluid channel that is connected to the further fluid opening. One of the fluid channels is connected to the high-pressure side and the other fluid channel to the low-pressure side of a fluid supply. The fluid supply can be a pressure source during motor operation and a corresponding connection to the hydraulic consumer during pump operation. The fluid openings serve as hydraulic control windows for the piston engine by determining when the working chambers are connected to the high-pressure side or the low-pressure side during one revolution, i.e. in one cycle. For a hydraulic transformer, a third fluid opening connected to a third fluid channel can be provided. The third fluid channel can therefore be used for the work connection.

[0030] The invention can be used particularly advantageously in radial piston engines with at least three pistons, especially with nine pistons. This allows a sufficiently large effect and the most uniform pressure distribution possible in the working chambers to be achieved.

[0031] Advantages for manufacturing and assembly arise when the drive shaft and the sliding body are formed as a single piece. This ensures that the polygonal cone is aligned with the drive shaft. The efficiency of the piston engine can be further improved if the pistons have a fluid pocket for hydrostatic bearings at the contact surface with the sliding surface and if the pistons have a longitudinal bore through which fluid from the cylinder's working chamber flows into the fluid pocket. This hydrostatic bearing can reduce friction losses when the pistons slide on the sliding surfaces of the sliding body.

[0032] Efficiency can be further improved by providing a fluid pocket for hydrostatic bearings on the cylinder block for each cylinder at the contact surface with the control body. This also reduces friction during the rotational movement of the cylinder body on the control body.

[0033] By appropriately designing the fluid pockets on the cylinder body and the piston, hydrostatic compensation of the forces can be achieved, so that internal friction is minimized.

[0034] In an alternative embodiment, the lifting machine according to the invention can be designed such that the piston and cylinder are interchanged. The invention also relates to a hydraulic, stroke-adjustable piston machine comprising a housing, a drive shaft rotatably mounted therein with an annular sliding body having a plurality of polygonally arranged sliding surfaces on its inner side, as well as a plurality of cylinders, each of which is supported on one of the sliding surfaces, and each cylinder having an associated piston which can move back and forth in the respective cylinder, wherein the pistons together form a piston star, and wherein a fluid-filled working chamber delimited by the piston is formed in each cylinder, further comprising a control body having a control pin on or with which the cylinder star can rotate about the control pin axis; wherein the piston machine is designed such thatthat the cylinders, and with them the piston star, are rotated by the sliding body upon rotation of the drive shaft, and wherein the control body is linearly displaceable along a control line such that the control pin can be adjusted eccentrically to the shaft, so that upon rotation of the drive shaft about the shaft axis and rotation of the cylinder block about the pin axis, the working chamber in the cylinder cyclically increases and decreases, and the respective working chambers are cyclically connected, one after the other, to a first fluid opening and another fluid opening via a bore in the piston. The embodiment according to the invention is characterized in that the sliding body is designed as a polygonal cone with a cone angle α, which indicates the orientation of the sliding surfaces to the shaft axis, and in that the control line is arranged at a control angle β to the pin axis, wherein the cone angle α and the control angle β both lie in the range between 15° and 80°.and where cone angle a and control angle ß have a maximum difference of 3°.,

[0035] The advantages and detailed features described above can also be advantageously implemented in this alternative design.

[0036] Further advantageous features of the invention are explained using exemplary embodiments with reference to the drawings. These features can be advantageously implemented not only in the illustrated combination, but also individually combined with one another. The figures show in detail:

[0037] Fig.1 a Piston engine according to the invention

[0038] Fig.lb Longitudinal section

[0039] Fig.2a Drive shaft with sliding body

[0040] Fig.2b Control body (side view, front view, isometric)

[0041] Fig.3a Cylinder block

[0042] Fig.3b View of cylinder block installed (without control body)

[0043] Fig.4a Longitudinal section of the pistons and cylinders in detail

[0044] Fig.4b Conic section view along AA on piston and cylinder

[0045] Fig.5 Longitudinal section at zero stroke setting

[0046] Fig.6 Alternative inventive design of the piston engine

[0047] Fig. 7 Schematic diagram for another control line. The figures are described in more detail below. Like reference numerals denote like or analogous parts or components.

[0048] Fig. 1a shows an inventive embodiment of the hydraulic, stroke-adjustable piston engine 1. The housing 2 and the further housing 3 enclose the components. The drive shaft 10 is mounted in the housing 2. And the control body 20 is guided in the further housing 3. Two connections for the fluid are provided on the control body 20. Depending on how the piston engine is operated, one fluid connection can be the high-pressure side and the second fluid connection the low-pressure side, or vice versa. And depending on the operating mode, the high-pressure side can be the oil supply and the low-pressure side the oil discharge (motor operation) or the high-pressure side is the oil discharge and the low-pressure side the oil supply (pump operation). When operated as a hydraulic piston motor, the drive shaft 10 is driven by the fluid supply. When operated as a hydraulic piston pump, the rotation of the drive shaft 10 pumps the fluid from the low-pressure side to the high-pressure side.

[0049] Fig. 1b / Fig. 4a and Fig. 5 show the piston engine 1 in longitudinal section. The design shown here is an internally loaded diagonal piston engine with eight pistons. Generally, an odd number of pistons is advantageous, and a design with at least seven pistons is particularly advantageous. To better understand the function, an even number of pistons has been chosen here.

[0050] The more pistons there are, the smoother the running and the greater the efficiency. The odd number of pistons offers the advantage that no two pistons pass through top dead center (TDC) and bottom dead center (BDC) at the same time. This reduces pulsation.

[0051] The drive shaft 10 is mounted in the housing 2 via bearings 4, 5 and is rotatable about the shaft axis 6. Connected to the drive shaft 10 is the sliding body 11, which is designed as a polygonal cone. This means that the sliding body is conical with the cone line 9, which is aligned with the shaft axis 6 at a cone angle α. The sliding surfaces 12 are arranged on the inside of the sliding body cone and are aligned parallel to the cone line 9.

[0052] The piston engine 1 comprises several pistons 32, each of which can move back and forth in a cylinder 31. Each piston 32 rests on a sliding surface 12. The sliding body 11 has as many sliding surfaces 12 as there are pistons 32 or cylinders 31. The cylinders 31 are combined to form a cylinder block 30, also called a cylinder star. The cylinder block 30 has a central bore as a receptacle 33 for the control pin 21. The control pin 21 serves as a guide and axis of rotation for the cylinder block 30. The cylinder block 30 rotates about the pin axis 7, with the inner sliding surface 37 of the cylinder block 30 sliding on the control piston sliding surface 29 of the control body 20.

[0053] A working chamber for the fluid is provided between piston 32 and cylinder 31. The cylinders 31 rest with a surface on the respective sliding surface 12 of the sliding body 11. The cylinder body 30 has an opening 34 on the inner surface of each cylinder 31, which allows the fluid to be supplied to or discharged from the working chamber. When the sliding body 11 rotates in the housing 2, the pistons 32 are carried along by the polygonally arranged sliding surfaces 12 and also rotate about the shaft axis 6. The pistons carry the cylinders 31 along and thus also set the cylinder block 30 in rotation. However, this rotates about the journal axis 7. When the cylinder block 30 rotates, the working chambers in the cylinder 31 are cyclically connected one after the other to the first fluid opening 22 and the further fluid opening 23 in the control body.

[0054] The control body 20 comprises the control pin 21, which determines the position of the pin axis 7 and thus the eccentricity e for the rotation of the cylinder block 30. The control body 20 is guided in the further housing 3. And it is continuously linearly displaceable along the control line 8. The displacement is achieved via the hydraulically actuated control piston 24, which is housed in the control piston housing 25 and can be adjusted via the pressure in the control piston chambers 26. The control piston is preferably designed as a double-acting hydraulic piston. In general, other controls for displacing the control body are also possible, e.g., electrically or pneumatically.

[0055] If the control body 20 is now moved along the control line 8, the control pin 21 and with it the axis of rotation of the cylinder block 30 moves. The control line 8 forms the control angle ß with the pin axis 7. During the displacement it is important that the pin axis 7 is always aligned essentially parallel to the shaft axis 6. A deviation of up to + / - 3° can be regarded as essentially parallel. By moving the control body 20, the eccentricity e and thus the stroke of the piston in the cylinder can be adjusted. The greater the eccentricity e, the greater the stroke that the piston moves back and forth in the cylinder during one revolution.

[0056] Due to the eccentricity e, the height h of the working space in the cylinder 31 changes during one revolution of the sliding body 11 and the cylinder block 30. At bottom dead center BDC (top in this illustration) the working space is at its largest and at top dead center TDC (bottom in the illustration) the working space is at its smallest.

[0057] During operation, the volume of the working chamber thus changes cyclically, generating the pumping effect from the drive shaft on the fluid or the driving effect from the fluid on the drive shaft. The respective piston 32 slides cyclically back and forth on the sliding surface 12, with the cylinders 31 and the pistons 32 always remaining exactly coaxial, and the pistons 32 always positioned exactly perpendicular to the respective sliding surface 12. This prevents any tilting or pendulum movement. Since no transverse forces act on the cylinders 31, they can be designed with much thinner walls and thus lighter weight.

[0058] The first fluid channel 27 and the second fluid channel 28 are integrated in the control body 20, with the first fluid channel 27 being connected to the first fluid opening 22 and the second fluid channel 28 being connected to the further fluid opening 23. In the side view, the second fluid channel 28 is located behind the first fluid channel 27. This integration in the control body 20 enables a very compact design of the piston engine.

[0059] The eccentricity e can be continuously adjusted from the zero stroke point up to the maximum. The illustration in Fig. 1b is close to the maximum stroke.

[0060] The diagonal arrangement of the pistons 32 and cylinders 31 makes the arrangement much more compact and also simplifies production and assembly. Furthermore, the arrangement is less sensitive to temperature differences. In the illustrated embodiment, the cone angle α and the control angle β are in the range of 45°. To utilize the advantages of the invention, they should be between 15° and 80°, preferably between 30° and 60°.

[0061] Fig. 5 shows the piston engine 1 at zero stroke, meaning the eccentricity e is zero. Shaft axis 6 and journal axis 7 are aligned. With one rotation of the cylinder block 30, the volume of the working chamber does not change. The pumping effect is thus zero, even when the drive shaft 10 rotates.

[0062] The cone angle α and control angle β are both in the range between 30° and 60°, preferably between 40° and 50°. This allows the advantages of the inventive design to be fully realized.

[0063] The illustration in the figures shows a particularly preferred embodiment in which the cone angle α and the control angle β are the same and both equal to 45°. As a result, the displacement of the control body 20 is transferred directly 1:1 to the height h of the working chamber at bottom dead center BDC, since the longitudinal axis of the piston at bottom dead center BDC lies in line with the control line 8. At the same time, the longitudinal axis L of the piston at top dead center TDC is perpendicular to the control line 8, so that the height h at top dead center TDC is not changed at all by the displacement of the control body. The dead volume is therefore not increased when the piston engine is running in partial stroke operation. In this way, the advantages of the invention can be utilized particularly well. Fig. 2a shows the drive shaft 10 with the sliding body 11, which is designed as a polygonal cone. The sliding body 11 has the sliding surfaces 12 on its inside, which are arranged in a polygonal manner and each parallel to the cone line 9.

[0064] Fig. 2b shows the control pin 20 in three different views - a side view, a front view, and an isometric view. The control body 20 comprises the control pin 21 and the control piston 24. In its front area, it is rectangular to enable more precise guidance in the further housing 3. Furthermore, the control body 20 has the first fluid opening 22, as well as the adjoining first fluid channel 27 integrated into the interior, and the further fluid opening 23 with the adjoining further fluid channel 28 integrated into the interior. One of the fluid channels 27, 28 is connected to the high-pressure side and the other to the low-pressure side of a corresponding fluid supply. The first fluid opening 22 and the further fluid opening 23 serve as control windows for the piston engine, with which it is determined in which angular position of the cylinder block 30 the cylinders 31 are connected to the high-pressure side or to the low-pressure side.

[0065] Fig. 3a shows the cylinder block 30. The central receptacle 33 for the control pin is in the middle, and the cylinders 31 are arranged around it inside the cylinder block. Each cylinder 31 has a cylinder opening 34 on the inside, which opens into an intermediate space. Depending on the rotational angle, this intermediate space is covered either by the first fluid opening 22 or by the further fluid opening 23 - or briefly by the control piston sliding surface 29 of the control pin. By designing the intermediate spaces around the cylinder openings 34 and the first and further fluid openings 22, 23, the flow and pressure curve during one revolution can be precisely shaped.

[0066] Fig. 3b shows a view of the cylinder block 3 when the control body 20 and the other housing 3 are removed. The polygonal shape of the sliding body 11 and the corresponding arrangement of the cylinders 31 and the pistons 32 are clearly visible.

[0067] Fig. 4a is an enlarged detail of Fig. 1. To reduce internal friction losses and thus further increase the efficiency of the piston engine 1, a fluid pocket 36 for hydrostatic bearings is preferably provided on each piston 32. This fluid pocket 36 is supplied with fluid via a longitudinal bore in the piston 32, which connects the working chamber of the cylinder with the fluid pocket 36. This reduces the friction between the piston 32 and the sliding surface 12.

[0068] Another fluid pocket, which also serves as an intermediate space 35, is provided on the inside of the cylinder block 30 below each of the cylinders 31. This serves to control the pressure distribution as described above, and also reduces the friction between the inner surface 37 and the control piston sliding surface 29 on the control pin.

[0069] Since the sliding surfaces 12 on the sliding body 11, i.e., the polygonal cone, and the control piston sliding surface 29 on the control body 20 are each arranged in a conical shape, the piston engine 1 is less sensitive to distortion due to different thermal expansion. Such expansion, which can occur, for example, with very different fluid temperatures, is hydrostatically compensated in the diagonal piston pump.

[0070] Fig. 4b shows a conical section running along line AA in Fig. 4a. As a result, the pistons 32 now lie in one plane. The cyclical volume change of the working chamber in the cylinder 31 can thus be clearly seen. Also visible is the arrangement of the first and further fluid openings 22, 23, which serve as control windows and are connected to the first and further fluid channels 27, 28. Furthermore, one can see how the pistons 32 slide back and forth on the respective sliding surface 12 depending on their position. Overall, the diagonal piston machine 1 is therefore very space-saving and compact. Due to the low rotating masses of the components, the internal inertia of the piston machine 1 is low. In addition, friction losses are minimized. The design according to the invention enables significantly higher efficiency than with known piston machines.

[0071] Fig. 6 shows an alternative embodiment of the piston engine 1a according to the invention, in which the pistons 42 and cylinders 41 have been interchanged compared to the previously described variants. It is still internally pressurized, such that the fluid channels are connected to the working chamber via the bore 43 in the piston. The cylinders 41 are supported on the sliding surfaces 12 of the sliding body, and the pistons 42 are combined to form a piston star 40, which is supported on the control body sliding surface 29.

[0072] All other functions and features are analogous to the previous versions. The individual detailed features described there can also be implemented just as advantageously in the alternative version.

[0073] Fig. 7 shows a schematic representation of how four-quadrant operation is possible with a piston engine 1,T according to the invention. For this purpose, the guide for the control body 20 is designed in such a way that it is not only linearly adjustable along the control line 8, but is also linearly adjustable from the neutral position at zero stroke along the further control line 8a. The further control line 8a is also inclined by the angle ß relative to the journal axis, but in a mirrored, i.e. negative, direction to the control line 8. The journal axis 7 is shown in the neutral position with zero stroke. 7' and 7" indicate further positions for the journal axis 7 when the journal axis is adjusted along the control line 8 or along the control line 8a.

[0074] Thus, the stroke of the pistons 32, 42 can be shifted from the maximum stroke position by the control body 20 along the control line 8 to the zero stroke position. And then, from the zero stroke position along the control line 8a, the stroke of the pistons can be increased in the other direction.

[0075] List of reference symbols

[0076] 1 , 1 ' piston engine

[0077] 2 housings

[0078] 3 additional housings

[0079] 4 camps

[0080] 5 warehouses

[0081] 6 Shaft axis

[0082] 7 Pin axis

[0083] 8 Control line

[0084] 8a additional control line

[0085] 9 Cone line

[0086] 10 Drive shaft

[0087] 11 sliding bodies

[0088] 12 Sliding surface

[0089] 20 control bodies

[0090] 21 control pins

[0091] 22 first fluid opening

[0092] 23 additional fluid opening

[0093] 24 control pistons

[0094] 25 control piston housing

[0095] 26 Control piston chamber

[0096] 27 first fluid channel

[0097] 28 additional fluid channel

[0098] 29 Control piston sliding surface

[0099] 30 cylinder block

[0100] 31 cylinders

[0101] 32 pistons

[0102] 33 Holder for control pin

[0103] 34 Fluid opening

[0104] 35 Interspace / Fluid pocket

[0105] 36 Fluid pocket 37 Inner surface

[0106] 40 piston star

[0107] 41 cylinders

[0108] 42 Piston 43 Bore e Eccentricity h Height of the working chamber

[0109] L Longitudinal axis of the piston TDC Top dead center

[0110] UT Bottom dead center a Cone angle ß Control angle

Claims

Patent claims 1. A hydraulic, stroke-adjustable piston engine (1) comprising a housing (2), a drive shaft (10) rotatably mounted therein, with an annular sliding body (11) having a plurality of polygonally arranged sliding surfaces (12) on its inner side, as well as a plurality of pistons (32), each of which is supported on one of the sliding surfaces (12), and an associated cylinder (31) for each piston (32), in which the respective piston (32) can move back and forth, wherein the cylinders (31) together form a cylinder block (30), and wherein a fluid-filled working chamber delimited by the piston (32) is formed in each cylinder (31), further comprising a control body (20) having a control pin (21) on or with which the cylinder block (30) can rotate about the control pin axis (7); wherein the piston engine (1) is designed such thatthat the pistons (32) and with them the cylinder block (30) are rotated by the sliding body (11) upon rotation of the drive shaft (10), and wherein the control body (20) is linearly displaceable along a control line (8) such that the control pin (21) can be adjusted eccentrically to the shaft (10), so that upon rotation of the drive shaft (10) about the shaft axis (6) and rotation of the cylinder block (30) about the pin axis (7), the working space in the cylinder (31) becomes cyclically larger and smaller, and the respective cylinders (31) are connected cyclically and alternately one after the other via a cylinder opening (34) to a first fluid opening (22) and a further fluid opening (23), characterized in that the sliding body (11) is designed as a polygonal cone with a cone angle α, which indicates the orientation of the sliding surfaces (12) to the shaft axis (6), and that the control line (8) is in a Control angle ß to the pin axis (7) is arranged,where the cone angle a and the control angle ß are both in the range between 15° and 80°, and where the cone angle a and the control angle ß have a maximum difference of 3°.

2. Hydraulic piston machine (1) according to claim 1, characterized in that the cone angle α and the control angle β are both in the range between 30° and 60°, preferably between 40° and 50°, and in particular at 45°.

3. Hydraulic piston machine (1) according to one of claims 1 or 2, characterized in that the cone angle α and the control angle β differ by less than 5°, in particular that they are of equal size.

4. Hydraulic piston machine (1) according to one of the preceding claims, characterized in that the radial piston machine (100) is designed such that it can work both as a radial piston pump and as a radial piston motor, and can work in the so-called four-quadrant operation, that is to say that it can drive the drive shaft (10) in both directions of rotation, and that the pumping action can take place both from the first fluid opening (22) to the further fluid opening (23) and in the opposite direction.

5. Hydraulic piston machine (1) according to one of the preceding claims, characterized in that the cylinders have a circular cross-section and the diameter of the cylinders (32) is between 3 mm and 100 mm.

6. Hydraulic piston machine (1) according to one of the preceding claims, characterized in that the control body (20) has in its interior a first fluid channel (27) which is connected to the first fluid opening (22) and a further fluid channel (28) which is connected to the further fluid opening (23), one being connected to the high-pressure side and one to the low-pressure side of a fluid supply.

7. Hydraulic piston machine (1) according to one of the preceding claims, characterized in that the maximum displacement of the control body (20) along the control line (8) is at least 3 mm and a maximum of 100 mm.

8. Hydraulic piston machine (1) according to one of the preceding claims, characterized in that at least three pistons (32), in particular that nine pistons (32) are present.

9. Hydraulic piston machine (1) according to one of the preceding claims, characterized in that the drive shaft (10) and the sliding body (11) are formed in one piece.

10. Hydraulic piston machine (1) according to one of the preceding claims, characterized in that a further housing (3) is provided which is connected to the housing (2) and in which the control body (20) is guided, in particular in a bushing.

11. Hydraulic piston machine (1) according to one of the preceding claims, characterized in that the pistons (32) have a fluid pocket for hydrostatic mounting on the contact surface with the sliding surface (12) and that the pistons (32) have a longitudinal bore through which fluid from the working chamber of the cylinder (31) passes into the fluid pocket.

12. Hydraulic piston machine (1) according to one of the preceding claims, characterized in that the cylinder block (30) has a fluid pocket for hydrostatic mounting on the contact surface to the control body (20) for each cylinder.

13. A hydraulic, stroke-adjustable piston engine (1) comprising a housing (2), a drive shaft (10) rotatably mounted therein, with an annular sliding body (11) having a plurality of polygonally arranged sliding surfaces (12) on its inner side, and a plurality of cylinders (41) each supported on one of the sliding surfaces (12), and each cylinder (41) having an associated piston (41) which can move back and forth in the respective cylinder (41), wherein the pistons (42) together form a piston star (40), and wherein a fluid-filled working chamber delimited by the piston (42) is formed in each cylinder (41), further comprising a control body (20) having a control pin (21) on or with which the cylinder star (40) can rotate about the control pin axis (7); wherein the piston engine (1) is designed such thatthat the cylinders (41) and with them the piston star (40) are rotated by the sliding body (11) upon rotation of the drive shaft (10), and wherein the control body (20) is displaceable linearly along a control line (8) such that the control pin (21) can be adjusted eccentrically to the shaft (10), so that upon rotation of the drive shaft (10) about the shaft axis (6) and rotation of the cylinder block (30) about the pin axis (7), the working space in the cylinder (41) becomes cyclically larger and smaller, and the respective working spaces are connected cyclically and alternately one after the other via a bore (43) in the piston to a first fluid opening (22) and a further fluid opening (23), characterized in that the sliding body (11) is designed as a polygonal cone with a cone angle a, which indicates the orientation of the sliding surfaces (12) to the shaft axis (6), and that the control line (8) is at a control angle ß to the pin axis (7),where the cone angle a and the control angle ß are both in the range between 15° and 80°, and where the cone angle a and the control angle ß have a maximum difference of 3°.

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