EP3019702B1 - Axial piston machine - Google Patents

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 points on the outer or inner circumference of the annular swash plate, which engages in an elongated, curved extending projection of the housing or a component connected to the housing. 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. Thereby arise 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 which the different speed profiles of the piston movements can have on the filling of the cylinders 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 re-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. Fig. 8 )) 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. It can, if the phase relationship between inlet and outlet of all cylinders may be constant, only one (combined) inlet and outlet opening per cylinder 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.

Fig. 1:

eine Ausführungsform eines erfindungsgemäßen Axialkolbenmotors in einer perspektivischen Darstellung;

Fig. 2:

den Axialkolbenmotor in einer Draufsicht;

Fig. 3:

den Axialkolbenmotor in einem Schnitt entlang der Ebene III - III in Fig. 2;

Fig. 4:

den Axialkolbenmotor in einem Schnitt entlang der Ebene IV - IV in Fig. 2;

Fig. 5:

einen vergrößerten Ausschnitt des Axialkolbenmotors in einem Schnitt entlang der Ebene V - V in Fig. 2;

Fig. 6:

den Drehschieber des Axialkolbenmotors in einer perspektivischen Darstellung;

Fig. 7:

den Drehschieber in einer Ansicht von oben;

Fig. 8:

den Drehschieber in einer Ansicht von unten;

Fig. 9:

den Drehschieber in einem Schnitt entlang der Ebene IX - IX in Fig. 7;

Fig. 10:

den Drehschieber in einem Schnitt entlang der Ebene X - X in Fig. 7;

Fig. 11:

den Drehschieber in einem Schnitt entlang der Ebene XI - XI in Fig. 7;

Fig. 12:

die Zylinderkopfplatte des Axialkolbenmotors in einer Draufsicht;

Fig. 13:

eine Taumelscheibe für eine erfindungsgemäße Axialkolbenmaschine in einer Draufsicht;

Fig. 14:

den Verlauf der Kolbenbewegungen bei einer gattungsgemäßen Axialkolbenmaschine mit sechs Zylindern;

Fig. 15:

den Verlauf der Zylinderfüllungen bei einer gattungsgemäßen Axialkolbenmaschine mit sechs Zylindern; und

Fig. 16:

den Verlauf der Zylinderfüllungen bei einer erfindungsgemäßen Axialkolbenmaschine mit sechs Zylindern.

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

Fig. 1:

an embodiment of an axial piston according to the invention in a perspective view;

Fig. 2:

the axial piston motor in a plan view;

3:

the axial piston motor in a section along the plane III - III in Fig. 2 ;

4:

the axial piston motor in a section along the plane IV - IV in Fig. 2 ;

Fig. 5:

an enlarged section of the axial piston motor in a section along the plane V - V in Fig. 2 ;

Fig. 6:

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

Fig. 7:

the rotary valve in a view from above;

Fig. 8:

the rotary valve in a view from below;

Fig. 9:

the rotary valve in a section along the plane IX - IX in Fig. 7 ;

Fig. 10:

the rotary valve in a section along the plane X - X in Fig. 7 ;

Fig. 11:

the rotary valve in a section along the plane XI - XI in Fig. 7 ;

Fig. 12:

the cylinder head plate of the axial piston motor in a plan view;

Fig. 13:

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

Fig. 14:

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

Fig. 15:

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

Fig. 16:

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

The Fig. 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, which forms a plurality (in this case six) of cylinders 12 which are aligned parallel to one another and extend through the entire cylinder body 10. In each of the cylinders 12, a piston 14 is movably guided. The pistons 14 are connected via a connecting rod 16 with an annular swash plate 18. The swash plate 18 is rotatably mounted on a swash plate 20 which is rotatably connected to a (output) shaft 22 of the axial piston motor.

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

The pressure of the successively entering into the individual cylinder 12 working medium leads due to the inclination of the swash plate 18 to a directed in the circumferential direction force component in the connection points of the connecting rod 16 at the Swashplate 18. This force component causes the desired rotation of the shaft 22. As a result of the rotation of the shaft 22 and the rotatably connected swash plate 20, the swash plate 18 is placed in a tumbling motion, leading to an up and down movement of the with the swash plate 18th via the connecting rod 16 connected piston 14 leads. In this case, each of the pistons 14 cyclically moves between a top dead center (TDC) and a bottom dead center (TDC).

The pistons 14 work with two clocks. The movement between the TDC and the TDC of each piston 14 is effected by the working medium flowing into the respective cylinders 12 (working stroke). In the guided by the swash plate 18 movement of the piston 14 between the UT and the TDC, the relaxed working fluid from the respective cylinders 12 is ejected (exhaust stroke). The inflow and expulsion of the working fluid at the designated timing is realized by means of intake and exhaust valves for each of the cylinders 12 formed by a rotary valve device.

The rotary valve device comprises a cylinder head plate 26 which abuts the cylinder body 10 on the front side on the side remote from the swash plate 18. The cylinder head plate 26 has a combined intake and exhaust port 28 for each of the cylinders 12 (see FIG. Fig. 12 ). Further openings 30 are used to receive screws 32, through which a housing head 34, the cylinder head plate 26, the cylinder body 10 and a swash plate 18 and the swash plate 20 surrounding housing 36 are interconnected. On the cylinder head plate 26 is a rotary valve 38, which is rotatably connected to the shaft 22 and thus rotates relative to the cylinder head plate 26 during operation of the axial piston motor. Characterized the inlet and outlet openings 28 of the cylinder head plate 26 are alternately and once per revolution of the shaft 22 in registration with an inlet port 40 and with an outlet opening 42 of the rotary valve 38 is brought. The inlet opening 40 and the outlet opening 42 are arranged on the same circular path around the center (the axis of rotation) of the rotary valve 38. In the event of an overlap with the inlet opening 40, the vaporous working medium is supplied to the respective cylinder 12 via a central inlet 44 and a radially extending inlet channel 46 integrated into the rotary valve 38. When overlapping with the outlet opening 42, the working fluid is expelled from the respective cylinder 12 and discharged through outlets 48 from the axial piston motor. In this case, 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) is selected such that an overlap (and thus Inlet valve opening) with the inlet and outlet opening 28 is always given only a cylinder 12, while the much longer (only interrupted by reinforcing struts 60) outlet opening 42 of the rotary valve 38, a simultaneous opening of several outlet valves (by covering with the corresponding inlet and outlet openings 28th the cylinder head plate 26) provides.

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

In order to prevent the swash plate 18 from being carried along by the rotational movement of the swashplate base 20, it is provided to connect it to the cylinder body 10 in a rotationally fixed manner (relative to the axis of rotation of the shaft 22). For this purpose, a securing sleeve 52 is provided which is non-rotatably connected via securing pins 54 (with respect to the axis of rotation of the shaft 22) to the cylinder body 10. The securing sleeve 52 is also connected via a cardan-like joint arrangement with the swash plate 18. The hinge assembly 18 rotatably binds the swash plate 18 (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 joint arrangement comprises a joint ring 56, which is rotatable about a respective first axis about the two bearing pins 58 with the securing sleeve 52 (see FIG. Fig. 3 ) and about a second, perpendicular to the first axis extending axis rotatably with the swash plate 18 (see. Fig. 4 ) connected is.

In known, to the described axial piston engine according to the invention substantially functionally similar axial piston machines is provided to arrange the cylinder 12 in a uniform pitch in the cylinder body 10 and to provide a corresponding arrangement of the connection of the connecting rod 16 to the swash plate 18. In addition, identical inlet and outlet openings 28 are provided in the cylinder head plate 26 for the individual cylinders 12. This leads due to the rotationally fixed connection of the swash plate 18 with the cylinder body 10 to non-uniform piston movements and - resulting - to a nonuniform phase offset between adjacent piston 14. Thus, in an axial piston machine with six cylinders 12, the pitch between all adjacent cylinders 60 °. However, the phase offset of the piston movements, ie the partial rotation of the shaft 22, after the adjacent piston 14 each reach their TDC or UT, is not exactly 60 °, but up to a few degrees more or less.

The Fig. 14 visualizes this effect. There is shown over a revolution of the shaft 22, the movement of the six pistons 14 (solid lines). In addition, a sinusoidal comparison movement is entered with dashed line for each piston 14. The Fig. 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) Kolbenbewegungsverläufe on. Furthermore clarifies the Fig. 14 For example, based on the movement of the piston 14 reaching its TDC at 180 °, the phase offset to the movements of the two adjacent pistons is several degrees less than that due to the different phase offset from the pitch of 60 ° the 60 ° division expected 60 °. On the other hand, for the piston 14 which is in each case opposite in the cylinder body 10, the phase offset amounts to 180 ° in accordance with 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.

The phase offset between the movements of adjacent pistons 14 in conjunction with the symmetrical arrangement of intake and exhaust ports 28 in the cylinder head plate 26 of conventional axial piston engines results in the intake and exhaust valves not always exactly matching the intended position of the respective piston 14 (eg, at TDC). to open. This, as well as the different courses of the piston movements lead to a different filling of the cylinder 12, which remains at least some of the cylinder 12 below the intended filling. This results in a lower power and possibly also in a lower efficiency of the axial piston machine.

The Fig. 15 visualizes the differences in the filling of the individual cylinders 12 in a generic axial piston machine. There is over a revolution of the shaft 22, the course of the filling of the cylinder 12, that is, the change in the mass of the working fluid in the individual cylinders 12, shown. There, too, it appears that the course of the filling is the same (only 180 ° out of phase) only with cylinders 12 located opposite one another in the cylinder body 10.

In order to avoid this problem, it is provided in the axial piston engine according to the invention that the inlet and outlet openings 28 of the cylinder head plate 26 assigned to the individual cylinders 12 are individually adapted such that a substantially identical filling results for all cylinders 12 (cf. Fig. 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 selected such that all intake valves substantially always open in the TDC of the respective piston 14 (by an incipient overlap of the inlet and outlet openings 28 of 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 relative to the direction of the relative movement between the cylinder head plate 26 and the rotary valve 38 are different. As a result of the rotating relative movement of the rotary valve 38 and the cylinder head plate 26, the lengths of the inlet and outlet openings 28 are indicated as angular 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 Fig. 16 shows that according to the invention for all cylinders 12 substantially identical Füllungsverläufe can be realized.

Alternatively or additionally to an adaptation of the opening times of the inlet valves, it may also be provided to adapt 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 Fig. 13 shows a correspondingly formed swash plate 18, which in an axial piston according to the Fig. 1 to 11 can be used. It may be useful not only to adapt the pitches between the connections of the piston 14 to the swash plate 18, but also according to the pitches between adjacent cylinders 12 in the cylinder body 10, which may then be identical to that of the swash plate 18. An axial piston machine according to the invention with an adapted connection of the pistons 14 to the swash plate 18 can preferably be combined with adapted opening time of the individual valves, ie, for example, with respect to their length adapted inlet and outlet openings 28 in the cylinder head plate 26, so that in addition a compensation of the different waveforms of Piston movements can be done.

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

Claims (6)

1. Axial piston machine having a cylinder body (10), in which multiple cylinders (12) are formed, and having pistons (14) which are guided in movable fashion in the cylinders (12), wherein the pistons (14) are connected to a swashplate (18) which bears rotatably against a swashplate base (20), and wherein a fluid flow into and out of the cylinders (12) is controlled by means of inlet and outlet valves, characterized by varying pitches between the connections of the pistons (14) to the swashplate (18), and/or by opening times for the inlet and/or outlet valves which vary on a cylinder-selective basis.
2. Axial piston machine according to Claim 1, characterized in that the pitches are adapted such that adjacent pistons (14) always reach their TDC and/or BDC after a uniform partial rotation of the swashplate base (20).
3. Axial piston machine according to Claim 1 or 2, characterized in that the opening times are adapted such that the inlet and/or outlet valves of all the cylinders (12) open and/or close at identical piston positions of the associated pistons (14).
4. Axial piston machine according to one of the preceding claims, characterized in that the opening times are adapted such that the opening durations of the inlet and/or of the outlet valves of at least some of the cylinders (12) differ.
5. Axial piston machine according to Claim 4, characterized in that the different opening durations are adapted such that the masses of the partial quantities of fluid enclosed in the individual cylinders (12) in a cycle are as equal as possible.
6. Axial piston machine according to one of the preceding claims, characterized in that the inlet and/or the outlet valves comprise inlet and/or outlet openings (28) for the cylinders (12), which inlet and/or outlet openings are temporarily opened up and covered by means of a rotary slide (38), wherein the varying opening times are achieved by means of varying pitches between the inlet and/or outlet openings (28) of adjacent cylinders (12) and/or by means of varying lengths of the inlet and/or outlet openings (28).

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