DE102013213614A1 - axial piston - Google Patents

Abstract

An axial piston machine having a cylinder body (10) in which at least three cylinders (12) are formed and with pistons (14) movably guided in the cylinders (12), the pistons (14) being connected to a swash plate (18), which rotatably abuts a swashplate base (20), and wherein fluid flow into and out of the cylinders (12) is controlled by inlet and exhaust valves is by varying pitches between the connections of the pistons (14) to the swashplate (18) and / or varying opening times for the intake and / or exhaust valves.

Description

The invention relates to an axial piston machine and in particular to an axial piston motor for a cycle device for utilizing waste heat of an internal combustion engine.

Motor vehicles are currently mostly driven by internal combustion engines in which fuels are burned and the heat energy released thereby is partially converted into mechanical work. The efficiency of reciprocating internal combustion engines, which are used almost exclusively for driving motor vehicles, is about one third of the primary energy used. Thus, two-thirds of the thermal energy released during combustion is waste heat, which is released either via the engine cooling system or the exhaust system as heat loss to the environment.

Utilization of this waste heat represents a possibility to increase the overall efficiency of a drive unit of the motor vehicle and thus to reduce fuel consumption.

The DE 10 2008 028 467 A1 describes a device for using waste heat of an internal combustion engine. For this purpose, a first heat exchanger, the evaporator, a Dampfkreisprozessvorrichtung is integrated into the exhaust system of the internal combustion engine. The heat energy transferred in the heat exchanger from the exhaust gas to a working medium of the steam cycle device is partially converted into mechanical energy in an expansion device which can be used, for example, to assist the propulsion of a motor vehicle or to generate electrical energy. Downstream of the expansion device, the working medium is cooled in a second heat exchanger, the condenser, where it condenses. About a feed pump, an increase in pressure of the working medium and its supply to the evaporator.

As an expansion device in such a system for waste heat utilization, an axial piston motor can be used, as is known from DE 10 2010 052 508 A1 is known.

Axial piston engines have a cylinder body in which a plurality of cylinders are formed in a uniform pitch. In each of the cylinders, a piston is movably guided, wherein a phase offset is provided in the piston positions, which corresponds to the pitch between the cylinders with respect to a movement cycle of the piston ("piston cycle": OT → UT → OT or UT → OT → UT) , Through intake and exhaust valves, a pressurized fluid is successively introduced into the corresponding cylinder to exert a working stroke (OT → UT) of each piston, where appropriate (in the case of a pneumatic axial piston engine) expanding and causing movement of the respective piston. In an exhaust stroke (UT → OT) of each piston following the power stroke, the fluid is expelled again. The movements of the pistons are transmitted via an obliquely arranged to the longitudinal axes of the cylinder plate to which the pistons are connected directly or via connecting rods to an output shaft.

Axial piston compressors or pumps have a structure substantially identical to axial piston motors, wherein mechanical drive power is transmitted from the shaft via the obliquely arranged plate to the pistons and a rotational movement of the shaft or an associated drive motor is translated into the cyclical movement of the pistons , In the working stroke (UT → OT) of the individual pistons, a fluid previously introduced into the cylinder during an intake stroke (OT → UT) is displaced and / or compressed and expelled.

Axial piston machines (axial piston motors and axial piston compressors or pumps) are regularly executed in one of three designs.

In the swash plate and the bent axis design of the cylinder body rotates together with the piston. In the swashplate design, the shaft is arranged parallel to the cylinder body and rotatably connected thereto. The movement of the piston controlling oblique plate is fixed. In the oblique axis type, the longitudinal axes of the shaft, including the flange ("oblique plate") on which the pistons engage, and the cylinder are oblique to each other.

In the swash plate type, the cylinder body does not rotate with the pistons guided therein. The same applies to a swash plate to which the pistons are connected via connecting rods. The swash plate is rotatably mounted on a swash plate, wherein the support surface of the swash plate and thus the orientation of the swash plate is aligned obliquely with respect to the longitudinal axes of the cylinder. The swash plate is rotatably connected to the shaft.

In the case of axial piston machines of the swashplate type, it is regularly provided to ensure unintentional co-rotation of the swashplate with the swashplate base by means of a rotationally fixed fixation of the swashplate in or on the housing of the axial piston machine. For this purpose, a groove is regularly provided at one or more locations on the outer or inner circumference of the annular swash plate, in which an elongated, curved extending projection of the housing or one with the Housing connected component engages. These groove-protrusion connections prevent the swash plate from rotating, but at the same time allow it to move along the course of the protrusion, thereby allowing the tumbling motion of the swash plate.

The intake and exhaust valves of axial piston engines are regularly formed in the form of a rotary valve which is non-rotatably connected to the shaft and temporarily connects intake and exhaust ports of the individual cylinders to an intake and exhaust passage depending on the respective piston positions.

Based on this prior art, the present invention seeks to provide a Taumelscheibenbauart axial piston machine, which is characterized by the highest possible efficiency and / or a uniform course.

This object is achieved by an axial piston machine according to independent claim 1. Advantageous embodiments thereof are the subject of the dependent claims and will become apparent from the following description of the invention.

The invention is based on the finding that in an axial piston machine of the swash plate design as a result of fixing the swash plate to prevent rotation a nonuniformity in the wobbling motion is generated, which leads to a non-uniform phase offset in the piston positions of adjacent pistons and in a non-uniform velocity curve of adjacent pistons. This creates on the one hand rotational irregularities. On the other hand, the performance and efficiency of the axial piston machine is adversely affected, since the movement of individual pistons no longer fits exactly to the provided and provided by the rotational movement of the shaft valve timing. For example, it can be provided that the intake valves for all cylinders should be opened as exactly as possible at top dead center (TDC) of the respective piston. The inlet openings of all cylinders are arranged and formed identical with respect to the respective cylinders in conventional axial piston machines. Accordingly, the successive opening of the inlet openings takes place by the rotating with the shaft rotary valve after always the same, the division between the cylinders corresponding partial rotation of the shaft. The non-uniformity, which is introduced by the translation of the rotational movement of the shaft in the cyclic linear movement of the piston is not taken into account. This can thus lead to the inlet openings being opened by the rotary valve in individual cylinders before the associated piston reaches the TDC or after it has already passed the TDC. This leads to a deteriorated filling of these cylinders.

The basic idea of the invention is to compensate for the non-uniformity in the piston movements, which is due to the translation of the rotational movement of the shaft into the cyclical linear movement of the piston.

This is in a generic axial piston machine having a cylinder body in which a plurality (preferably at least three) cylinders are formed, as well as in the cylinders movably guided pistons, wherein the pistons are connected to a swash plate which rotatably bears against a swash plate, and wherein a fluid flow in and out of the cylinders is controlled by means of inlet and outlet valves, according to the invention achieved in that varying divisions between the (in particular fixed) connections of the piston to the swash plate and / or varying opening times for the inlet and / or outlet valves are provided ,

By varying the pitches of the connections of the piston to the swash plate, a translation of the total movement of the pistons, which is justified in the translation, can be compensated, so that, as a result, the pistons always reach their TDC and / or BDC after a constant partial rotation of the shaft.

By varying the opening times for the intake and / or exhaust valves, it is possible to ensure that, in spite of the nonuniformities in the piston movements caused by the translation, the opening times match the respective piston positions as exactly as possible.

In particular, it may be provided that the varying opening times are adapted such that the inlet and / or the exhaust valves of all cylinders open and / or close at identical piston position of the associated piston. Thereby, the filling of the cylinder and thus the performance and possibly also the efficiency of the axial piston machine can be improved. For example, it can be provided that the opening times of the intake valves of all cylinders are matched to the TDCs of the respective pistons by a cylinder-selective adaptation.

Furthermore, it can be provided that the varying opening times are adapted such that the opening duration of the inlet and / or outlet valves of at least some of the cylinders is different. As a result, in particular the influence that the different speed profiles of the piston movements on the filling of the Cylinder with the fluid can be compensated. Preferably, it is therefore provided that the different opening duration (ie the angular ranges of the part rotations of the shaft between the opening and the renewed closing of the inlet or outlet valves, defined by the sum of the respective angle α (length of the inlet and outlet openings 28 ) and the angle γ (length of the inlet opening of the rotary valve 38 , see. 8th )) is adapted such that the masses of the in each case a piston cycle in the cylinders enclosed subsets of the fluid are as equal as possible.

In a preferred embodiment of the axial piston machine according to the invention, provision may be made for the inlet and / or outlet valves to be in the form of a (multiple) rotary slide valve. Thus, the intake and / or exhaust valves may include intake and / or exhaust ports for the individual cylinders that are temporarily released and covered by a rotary valve. The varying opening times (and thus also varying opening duration of the individual intake and / or exhaust valves) can then be determined by a varying pitch between the inlet and / or outlet openings of individual cylinders and / or by different lengths (relative to the direction of movement relative to the rotary valve). the inlet and / or outlet openings of the cylinder can be achieved. In this case, provided that the phase relationship between inlet and outlet of all cylinders can be constant, only one (combined) inlet and outlet opening per cylinder can be provided. If different phase relationships between inlet and outlet are to be provided for the individual cylinders, at least one inlet and at least one outlet opening may be provided at different radii per cylinder, which are temporarily released by corresponding openings of the rotary valve.

The invention will be explained in more detail below with reference to exemplary embodiments illustrated in the drawings. In the drawings shows:

1 : An embodiment of an axial piston motor according to the invention in a perspective view;

2 : the axial piston engine in a plan view;

3 : the axial piston engine in a section along the plane III-III in 2 ;

4 : the axial piston engine in a section along the plane IV-IV in 2 ;

5 : An enlarged section of the axial piston motor in a section along the plane VV in 2 ;

6 : the rotary valve of the axial piston motor in a perspective view;

7 : the rotary valve in a view from above;

8th : the rotary valve in a view from below;

9 : the rotary valve in a section along the plane IX-IX in 7 ;

10 : the rotary valve in a section along the plane XX in 7 ;

11 : the rotary valve in a section along the plane XI-XI in 7 ;

12 : the cylinder head plate of the axial piston engine in a plan view;

13 : a swash plate for an axial piston machine according to the invention in a plan view;

14 : the course of the piston movements in a generic axial piston machine with six cylinders;

15 : the course of the cylinder fillings in a generic axial piston machine with six cylinders; and

16 : the course of the cylinder fillings in an axial piston machine according to the invention with six cylinders.

The 1 to 12 show an embodiment of an axial piston according to the invention in the form of an axial piston motor. The axial piston motor can be used, for example, in a cycle device for utilizing waste heat of an internal combustion engine of a motor vehicle. In this case, a vaporized and superheated and pressurized working medium expands in the axial piston motor, whereby part of the thermal and potential energy of the working medium is converted into mechanical energy.

The axial piston motor is designed in swash plate design. This comprises a cylinder body 10 of a plurality (here: six) of mutually parallel, extending through the entire cylinder body 10 extending cylinders 12 formed. In each of the cylinders 12 is a piston 14 movably guided. The pistons 14 are each about one pleuel 16 with an annular swash plate 18 connected. The swash plate 18 is rotatable on a swashplate base 20 stored, the rotation with a (driven) shaft 22 the axial piston motor is connected.

The swash plate 18 as well as the swashplate foot 20 have (coaxial) longitudinal axes which at a defined angle to the longitudinal axes (and the axis of rotation of the shaft 22 ) the cylinder 12 inclined. This angle is by means of an adjusting bolt 24 adjustable. This is provided with an external thread adjusting bolt 24 in a threaded opening of the shaft 22 guided.

The pressure of successively in the individual cylinder 12 entering working medium leads due to the inclination of the swash plate 18 to a circumferentially directed force component in the connection points of the connecting rods 16 on the swash plate 18 , This force component causes the desired rotation of the shaft 22 , As a result of the rotation of the shaft 22 and the thus rotatably connected swash plate foot 20 becomes the swash plate 18 in a staggering motion that leads to an up and down movement with the swash plate 18 over the connecting rods 16 connected pistons 14 leads. In doing so, each of the pistons moves 14 cyclically between a top dead center (TDC) and a bottom dead center (TDC).

The pistons 14 work with two bars. The movement between the OT and the UT of each piston 14 gets through that into the respective cylinder 12 inflowing working medium causes (power stroke). In the case of the swash plate 18 guided movement of the pistons 14 between the UT and the TDC, the relaxed working medium from the respective cylinders 12 ejected (ejection stroke). The inflow and expulsion of the working fluid at the scheduled timings is accomplished by means of intake and exhaust valves for each of the cylinders 12 realized that are formed by a rotary valve device.

The rotary valve device comprises a cylinder head plate 26 , which face the front of the swash plate 18 spaced side on the cylinder body 10 is applied. The cylinder head plate 26 has a combined inlet and outlet opening 28 for each of the cylinders 12 on (cf. 12 ). Other openings 30 serve to receive screws 32 through which a housing head 34 , the cylinder head plate 26 , the cylinder body 10 as well as the swash plate 18 and the swashplate foot 20 surrounding housing 36 connected to each other. At the cylinder head plate 26 is a rotary valve 38 on, the rotation with the shaft 22 is connected and thus in the operation of the axial piston motor relative to the cylinder head plate 26 rotates. This will cause the inlet and outlet openings 28 the cylinder head plate 26 alternately and once per revolution of the shaft 22 in overlap with an inlet opening 40 as well as with an outlet opening 42 of the rotary valve 38 brought. The inlet opening 40 and the outlet opening 42 are on the same orbit around the center (the axis of rotation) of the rotary valve 38 arranged. At a coverage with the inlet opening 40 becomes the respective cylinder 12 via a central inlet 44 and one in the rotary valve 38 integrated, radially extending inlet channel 46 fed to the vaporous working medium. At a coverage with the outlet opening 42 becomes the working medium from the respective cylinder 12 ejected and over outlets 48 removed from the axial piston motor. Here is the length of the inlet opening 40 of the rotary valve 38 (with respect to the direction of rotation relative to the cylinder head plate 26 ) selected such that an overlap (and thus inlet valve opening) with the inlet and outlet opening 28 always only one cylinder 12 given, while the much longer (only by reinforcing struts 60 interrupted) outlet opening 42 of the rotary valve 38 simultaneous opening of several outlet valves (by covering them with the corresponding inlet and outlet openings 28 the cylinder head plate 26 ).

The inlet channel 46 of the rotary valve 38 is designed for manufacturing reasons open to the outside. During assembly of the axial piston motor, this opening is made by means of a spherical closure body 50 closed (cf. 5 ).

To prevent the swash plate 18 from the rotational movement of the swash plate foot 20 is taken, is provided, this rotation (with respect to the axis of rotation of the shaft 22 ) with the cylinder body 10 connect to. This is a safety sleeve 52 provided, via safety pins 54 rotationally fixed (with respect to the axis of rotation of the shaft 22 ) with the cylinder body 10 connected is. The locking sleeve 52 is also a cardan-like joint arrangement with the swash plate 18 connected. The hinge assembly binds the swash plate 18 rotationally fixed (with respect to the axis of rotation of the shaft 22 ) to the locking sleeve 52 and thus to the cylinder body 10 , but at the same time allows the wobble of the swash plate. The hinge assembly comprises a hinge ring 56 , each with two bearing pins 58 rotatable about a first axis with the locking sleeve 52 (see. 3 ) and a second, to the first axis perpendicular axis rotatable with the swash plate 18 (see. 4 ) connected is.

In known, to the described axial piston engine according to the invention substantially functionally identical axial piston machines is provided, the cylinder 12 in even division in the cylinder body 10 to arrange and a corresponding arrangement of the connection of the connecting rod 16 on the swash plate 18 provided. In addition, identical inlet and outlet openings 28 in the cylinder head plate 26 for the individual cylinders 12 intended. This leads due to the rotationally fixed connection of the swash plate 18 with the cylinder body 10 to non-uniform piston movements and - as a result - to a non-uniform phase offset between adjacent pistons 14 , This is the case with an axial piston machine with six cylinders 12 the division between all adjacent cylinders 60 °. The phase offset of the piston movements, ie the partial rotation of the shaft 22 , after the adjacent piston 14 however, each reaching their OT or UT, but is not exactly 60 °, but up to a few degrees more or less.

The 14 visualizes this effect. There is over a turn of the wave 22 the movement of the six pistons 14 (solid lines) shown. Moreover, for every piston 14 entered a sinusoidal comparison movement with dashed line. The 14 shows that all real piston movements deviate from the respective sinusoidal comparison movement, wherein the deviations of the individual piston movements are also partially different. Only in the cylinder body 10 opposite, ie offset by 180 ° arranged piston 14 have identical (only 180 ° out of phase) piston movement curves. Furthermore clarifies the 14 the different, apart from the division of 60 ° phase offset in the movements of adjacent pistons 14 , For example, based on the movement of the piston reaching its TDC at 180 ° 14 , the phase offset to the movements of the two adjacent pistons several degrees less than the 60 ° due to the expected 60 ° division. For those in the cylinder body 10 each opposite piston 14 however, the phase offset is 180 ° according to the pitch. The non-uniformity and the phase offset in or between the piston movements tends to increase with increasing inclination angle of the swash plate 18 to.

The phase shift between the movements of adjacent pistons 14 in conjunction with the symmetrical arrangement of the inlet and outlet openings 28 in the cylinder head plate 26 conventional axial piston machines causes the inlet and outlet valves not always exactly to the intended position of the respective piston 14 (eg in OT) open. This as well as the different courses of the piston movements lead to a different filling of the cylinders 12 for at least some of the cylinders 12 below the intended filling remains. This results in a lower power and possibly also in a lower efficiency of the axial piston machine.

The 15 visualizes the differences in the filling of the individual cylinders 12 in a generic axial piston machine. There is over a turn of the wave 22 the course of filling the cylinder 12 , ie the change in the mass of the working medium in the individual cylinders 12 represented. Also there it shows that the course of the filling only in the cylinder body 10 opposite cylinders 12 is equal (only 180 ° out of phase).

To avoid this problem, it is provided in the axial piston motor according to the invention that the individual cylinders 12 associated inlet and outlet openings 28 the cylinder head plate 26 are individually adapted so that a substantially identical filling for all cylinders 12 results (cf. 12 ). It is provided on the one hand, that the division between the individual adjacent inlet and outlet openings 28 (relative to their central axes) may be different so that, for example, β ₁ ≠ β ₂ . In particular, the arrangement of the inlet and outlet openings 28 and thus the pitch is chosen such that all intake valves are always substantially in the TDC of the respective piston 14 open (by an incipient overlap of the inlet and outlet openings 28 the cylinder head plate 26 with the inlet opening 40 of the rotary valve 38 ). In addition, the lengths of the inlet and outlet openings 28 based on the direction of the relative movement between the cylinder head plate 26 and the rotary valve 38 differently. Due to the rotating relative movement of the rotary valve 38 and the cylinder head plate 26 are the lengths of the inlet and outlet openings 28 indicated as angle ranges. Thus, for example, α ₁ ≠ α ₂ . In principle, it may be provided that a longer opening duration should be provided for piston movements which are relatively flat in the region of their OTs, in order to achieve an identical filling in comparison to piston movements that are relatively acute in the OTs. The 16 shows that according to the invention for all cylinders 12 Essentially identical filling progressions can be realized.

Alternatively or additionally to an adaptation of the opening times of the inlet valves, it is also possible to provide the divisions between the connections of the connecting rods 26 to the swash plate 18 , whereby different phase shifts of the (total) movements of adjacent pistons 14 can be avoided. The 13 shows a correspondingly formed swash plate 18 , which in an axial piston motor according to the 1 to 11 can be used. It may be useful, not only the divisions between the connections of the piston 14 to the swash plate 18 but also according to the divisions between adjacent cylinders 12 in the cylinder body 10 , which then identical to that of the swash plate 18 could be. An axial piston machine according to the invention with an adapted connection of the pistons 14 to the swash plate 18 can preferably with adapted opening duration of the individual valves, ie, for example, in terms of their length adapted inlet and outlet openings 28 in the cylinder head plate 26 be combined, so that in addition a compensation of the different courses of the piston movements can take place.

LIST OF REFERENCE NUMBERS

10

cylinder body

12

cylinder

14

piston

16

pleuel

18

swash plate

20

Taumelscheibenfuß

22

wave

24

adjusting

26

Cylinder head plate

28

Inlet and outlet opening

30

opening

32

screw

34

housing head

36

casing

38

rotary vane

40

inlet port

42

outlet

44

inlet

46

inlet channel

48

outlet

50

closure body

52

securing sleeve

54

safety pin

56

joint ring

58

bearing pin

60

reinforcing strut

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008028467 A1 [0004]
• DE 102010052508 A1 [0005]

Claims (6)

Axial piston machine with a cylinder body ( 10 ), in which several cylinders ( 12 ) are formed, and with in the cylinders ( 12 ) movably guided pistons ( 14 ), the pistons ( 14 ) to a swash plate ( 18 ) which are rotatably attached to a swashplate base ( 20 ), and wherein fluid flow into and out of the cylinders ( 12 ) is controlled by means of inlet and outlet valves, characterized by varying divisions between the connections of the pistons ( 14 ) on the swash plate ( 18 ) and / or varying opening times for the intake and / or exhaust valves. Axial piston machine according to claim 1, characterized in that the pitches are adapted such that adjacent pistons ( 14 ) always after a constant partial rotation of the swash plate foot ( 20 ) achieve their OT and / or UT. Axial piston machine according to claim 1 or 2, characterized in that the opening times are adapted such that the intake and / or exhaust valves of all cylinders ( 12 ) at identical piston position of the associated piston ( 14 ) open and / or close. Axial piston engine according to one of the preceding claims, characterized in that the opening times are adapted such that the opening duration of the intake and / or the exhaust valves of at least some of the cylinders ( 12 ) is different. Axial piston machine according to claim 4, characterized in that the different opening duration is adapted such that the masses of the in one cycle in the individual cylinders ( 12 ) included subsets of the fluid are as equal as possible. Axial piston machine according to one of the preceding claims, characterized in that the inlet and / or the outlet valves inlet and / or outlet openings ( 28 ) for the cylinders ( 12 ), temporarily by means of a rotary valve ( 38 ), the varying opening times being characterized by varying divisions between the inlet and / or outlet openings (FIGS. 28 ) of adjacent cylinders ( 12 ) and / or by varying lengths of the inlet and / or outlet openings ( 28 ) is achieved.

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