Axial-piston motor and cyclic process device

Abstract

An axial piston motor having a cylinder housing, in which a plurality of cylinders are formed, and having pistons which are movably guided in the cylinders, wherein the pistons are attached to a swash plate and wherein a flow of a fluid that has entered via an inlet into the axial piston motor is controlled into and out of the cylinders by means of inlet and outlet valves, wherein the inlet and/or outlet valves comprise fluid change openings which are formed in a cylinder head plate and which can be temporarily released and covered by means of a rotary slide, for which purpose the rotary slide forms at least one passage opening.

Claims

1. An axial piston motor comprising: a cylinder housing, in which at least two cylinders are arranged; and at least two pistons that are movably guided in the cylinders, the pistons being attached to a swash plate, and wherein a flow of a fluid that has entered via an inlet into the axial piston motor is controlled into and out of the cylinders by means of inlet and outlet valves, wherein the inlet and/or outlet valves comprise fluid change openings, which are formed in a cylinder head plate and which can be temporarily released and covered by a rotary slide, for which purpose the rotary slide forms at least one passage opening, wherein the rotary slide comprises a sealing element that forms only a section of the lower side of the rotary slide, the side facing the cylinder head plate, and which is displaceably mounted in the direction of the cylinder head plate in or on a base body of the rotary slide.

2. The axial piston motor according to claim 1, wherein the base body of the rotary slide is arranged at least in sections spaced from the cylinder head plate.

3. The axial piston motor according to claim 1, wherein the sealing element on the side facing away from the cylinder head plate is acted upon directly or indirectly by the inlet pressure of the fluid.

4. The axial piston motor according to claim 3, further comprising one or more pressure pistons movably mounted in the base body of the rotary slide and bearing directly or indirectly against the sealing element, wherein the side, facing away from the sealing element, of the pressure piston or pistons is acted upon directly or indirectly by the inlet pressure of the fluid.

5. The axial piston motor according to claim 4, wherein a plurality of pressure pistons are provided which are arranged spaced in the circumferential direction with respect to the axis of rotation of the rotary slide, wherein the surfaces, exposed to the inlet pressure of the fluid, of these pressure pistons are formed as increasing in the intended direction of rotation of the rotary slide and/or the distances between at least three pressure pistons as decreasing in the intended direction of rotation.

6. The axial piston motor according to claim 1, wherein the sealing element extends over a circumferential section of 18020 with respect to the axis of rotation of the rotary slide.

7. The axial piston motor according to claim 1, wherein the sealing element extends over a circumference of 360 with respect to the axis of rotation of the rotary slide.

8. The axial piston motor according to claim 1, wherein the sealing element has a plurality of passage openings, of which at least one serves as an entry port and at least one as an exit port of the rotary slide.

9. The axial piston motor according to claim 1, wherein the sealing element is a partial or complete annular ring.

10. A cyclic process device comprising a circuit for a fluid, wherein an evaporator for evaporating the fluid, an expansion device for expanding the fluid, a condenser for condensing the fluid, and a conveying device for conveying the fluid in the circuit are integrated into the circuit, and wherein the expansion device is an axial piston motor according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus, are not limitive of the present invention, and wherein:

(2) FIG. 1 shows an embodiment of an axial piston motor of the invention (shown only in part) in a perspective view;

(3) FIG. 2 shows the axial piston motor in a longitudinal section;

(4) FIG. 3 shows the rotary slide of the axial piston motor in a perspective view;

(5) FIG. 4 shows the cover part, the sealing element, and the pressure pistons of the rotary slide in a perspective view;

(6) FIG. 5 shows a first radial section through the rotary slide;

(7) FIG. 6 shows a cross section through the rotary slide along the plane VI-VI in FIG. 5;

(8) FIG. 7 shows a second radial section through the rotary slide;

(9) FIG. 8 shows a top plan view of the cylinder head plate and the sealing element of the axial piston motor;

(10) FIG. 9 shows in a perspective view parts of an axial piston motor of the invention according to FIGS. 1 and 2 in an alternative embodiment of the sealing element;

(11) FIG. 10 shows a cyclic process device of the invention in a schematic illustration; and

(12) FIG. 11 shows a T-s diagram for a Clausius-Rankine process that can be performed by means of the cyclic process device.

DETAILED DESCRIPTION

(13) FIGS. 1 to 8 show an embodiment of an axial piston motor 10 of the invention. Axial piston motor 10 is designed as a swash plate type. For this purpose, it comprises a multipart cylinder housing 12 which comprises a plurality (here: six) of cylinder tubes 14 oriented parallel to one another. Cylinder tubes 14 limit cylinders 16 in each of which a piston 18 is movably guided. Pistons 18 are each attached via a connecting rod 20 to an annular swash plate 22. Swash plate 22 is rotatably mounted on a swash plate arm 24 which is nonrotatably connected to an (output) shaft 26 of axial piston motor 10.

(14) Swash plate 22 and swash plate arm 24 have (coaxial) longitudinal axes 28 which extend inclined at a defined angle to longitudinal axes 30, 32 of shaft 26 and cylinder 16.

(15) Due to the inclined position of swash plate 22, the pressure of the fluid (working medium) successively entering individual cylinders 16 leads to a circumferentially directed force component in the connection points of connecting rod 20 to swash plate 22, wherein this force component is transmitted to swash plate arm 24 and thereby causes the desired rotation of shaft 26. As a result of the rotation of shaft 26 and of swash plate arm 24 connected nonrotatably thereto, swash plate 22 is set into a wobbling motion, which leads to an up-and-down movement of piston 18 connected to swash plate 22 via connecting rod 20. In this case, each piston 18 moves cyclically between a top dead center (TDC), close to a cylinder head 36, and a bottom dead center (BDC), remote from cylinder head 36.

(16) The piston-cylinder units operate with two cycles. The movement of each piston 18 from the TDC to the BDC is brought about by the fluid flowing into the respective cylinders 16 (working stroke of the respective cylinder 16 and working stroke of the respective piston 18). In the case of the movement of pistons 18 guided by swash plate 22 from the BDC to the TDC, the fluid expanded during the preceding working stroke is expelled from the respective cylinders 16 (exhaust stroke of the respective cylinder 16 and exhaust stroke of the respective piston 18). The inflow and outflow of the fluid at the designated control times is controlled by inlet and outlet valves which are associated with cylinders 16 and which are formed as a combined rotary slide valve 38.

(17) Rotary slide valve 38 comprises a cylinder head plate 40 which on the front side lies against cylinder housing 12 sealingly on the side spaced from swash plate 22. Cylinder head plate 40 has in each case a fluid change opening 42, serving as a combined inlet and outlet opening, for each cylinder 16. Further openings 44 (see FIGS. 1 and 8) are used to receive screws 46 by which a cylinder head housing 48, cylinder head plate 40, cylinder housing 12, and a housing 50 surrounding swash plate 22 and swash plate arm 24 are interconnected. A rotary slide 52, which is connected nonrotatably to shaft 26 and thus rotates relative to cylinder head plate 40 during operation of axial piston motor 10, is disposed on the side of cylinder head plate 40, said side being spaced from cylinders 16. In this way, fluid change openings 42 of cylinder head plate 40 are made to overlap alternately and once per revolution of shaft 26 with a first passage opening (entry port) 54 and with a second passage opening (exit port) 56 of rotary slide 52. Entry port 54 and exit port 56 are located on the same circular path about rotation axis 32 of rotary slide 52. In the case of an overlapping of entry port 54, the gaseous fluid is supplied to the respective cylinder 16 via a central inlet 58 of axial piston motor 10, a cavity 60 integrated into rotary slide 52, and a fluid channel 62 connecting cavity 60 to entry port 54 (cf. FIG. 5). In the case of an overlapping with exit port 56, the fluid is expelled from the respective cylinders 16 and discharged out of axial piston motor 10 via an outlet 64. In this case, the length of entry port 54 of rotary slide 52 (with regard to the intended direction of rotation 72 of rotary slide 52) is selected such that there is an overlap with only fluid change opening 42 of a cylinder 16, whereas the considerably longer exit port 56 of rotary slide 52 provides for the simultaneous release of multiple fluid change openings 42.

(18) Rotary slide 52 and specifically a base body 66 of rotary slide 52 is designed in multiple parts for a design of cavity 60 that is advantageous in terms of manufacturing technology. It comprises a base part 68, which forms a central receiving recess into which a cover part 78 is inserted. Cover part 78 delimits cavity 60 with the upper side of base part 68 in the area of the receiving recess, wherein an opening in the circumferential surface of cover part 78 enables a fluid-conducting connection between cavity 60 and fluid channel 62.

(19) In addition to base body 66, rotary slide 52 comprises a sealing element 70, which in the exemplary embodiment according to FIGS. 1 to 8 is formed as a partially annular sealing plate which extends over a circumferential angle (with respect to the axis of rotation of the rotary slide) of approximately 180. Entry port 54 of rotary slide 52 is formed in this sealing element 70.

(20) In the embodiment of rotary slide 52 according to FIG. 9, in contrast, a complete, i.e., extending over a circumferential angle of 360, annular sealing element 70 (sealing plate) is provided, which in addition to entry port 54 forms a passage opening which is divided by structurally stabilizing partitions into multiple sections and which represents a section of exit port 56 formed by rotary slide 52.

(21) The closed sections (i.e., not forming entry port 54 and, in the exemplary embodiment according to FIG. 9, also not exit port 56) of sealing element 70 are used to cover fluid change openings 42 as needed, wherein at least the section located in the direction of rotation 72 of rotary slide 52 behind entry port 54, due to the nonrotatable coupling of rotary slide 52 via shaft 26 to swash plate arm 24, is always disposed such that it is located in the region of the three cylinders 16 in which the associated pistons 18 currently perform a working stroke during operation of axial piston motor 10.

(22) Sealing element 70 (in both exemplary embodiments) is movably disposed in a (partial) annular receiving recess, which is formed by the lower side of base body 66, said lower side being adjacent to cylinder head plate 40, wherein a displacement of sealing element 70, possible over a relatively small distance, is possible in the directions parallel to axis of rotation 32 of rotary slide 52 and thus toward cylinder head plate 40 or away from it. This enables sealing element 70 to be pressed against cylinder head plate 40 as needed, as a result of which fluid change openings 42, covered by the closed section of sealing element 70, are not only covered, but also the gap, formed between this section of sealing element 70 and cylinder head plate 40, is sealed sufficiently due to a sufficiently high force with which sealing element 70 is pressed against cylinder head plate 40.

(23) On the other hand, it is provided that the lower side of base body 66 is located at a defined, relatively small distance (e.g., about 3/10 mm) from the upper side of cylinder head plate 40, whereby contact between base body 66 and cylinder head plate 40 and thus friction losses due to the rotation of base body 66 relative to cylinder head plate 40 are prevented. Consequently, a contact between rotary slide 52 and cylinder head plate 40 is provided only in the areas of the sections, formed closed, of sealing element 70, whereby the size of this contact surface is reduced to the extent required for the sealed covering of fluid change openings 42 of cylinders 16 in which currently the associated pistons 18 perform a working stroke. As a result, friction losses resulting from the rotation of rotary slide 52 relative to cylinder head plate 40 are minimized. These friction losses can be kept particularly low if the materials from which cylinder head plate 40 (e.g., steel) and sealing element 70 (e.g., copper) are formed are also selected with regard to the lowest possible coefficient of friction. Furthermore, there is the possibility of coating cylinder head plate 40 and/or sealing element 70 with a friction-reducing plain bearing material (e.g., PTFE or DLC (diamond-like carbon)). Among other things, sealing element 70 can advantageously also be made of steel.

(24) Sealing element 70 is pressed against cylinder head plate 40 by means of multiple pressure pistons 74, which are arranged distributed along the sections, formed closed, and which are displaceably mounted (along axis of rotation 32) in a respective cylindrical receiving opening of base body 66 and which are acted upon on their upper side by the fluid flowing in via inlet 58 into cavity 60 of rotary slide 52 and thus by the inlet pressure of the fluid. For this purpose, in each case a fluid channel 62 leading to each pressure piston 74 is formed in base part 68 of base body 66 (cf. FIG. 7), which in each case has a fluid-conducting connection with cavity 60 via an associated opening 76 in the circumferential surface of cover part 78 (cf. FIG. 4). A sealing ring 80 (O-ring) is provided in each case to seal the circumferential gap between the circumferential surfaces of pressure pistons 74 and the boundary walls of receiving openings receiving these.

(25) Pressure pistons 74, acted upon by the inlet pressure of the fluid, press sealing element 70 against cylinder head plate 40, thereby achieving the previously described sealed covering of fluid change openings 42 of the cylinders 16 whose associated pistons 18 perform a working stroke. In this case, the force with which sealing element 70 is pressed against cylinder head plate 40 is directly dependent on the level of the fluid inlet pressure, so that at each actual inlet pressure level provided during operation of axial piston motor 10, on the one hand, a sufficient sealing is achieved and, on the other, an unnecessarily strong pressing of sealing element 70 against cylinder head plate 40 and thus an unnecessarily high frictional resistance for the rotation of rotary slide 52 relative to cylinder head plate 40 are prevented.

(26) In the case of sealing element 70 (of both embodiments), a closed section upstream of entry port 54 is provided, whose length in the circumferential direction corresponds at least to the width of fluid change openings 42 in the circumferential direction (cf. in particular FIGS. 8 and 9). This ensures that also if entry port 54 of sealing element 70 is only initially covered by the individual fluid change openings 42 of cylinder head plate 40, all of the fluid flowing into the respective cylinder 16 remains therein and does not flow out again via a gap which is still formed initially before sealing element 70. Pressing of sealing element 70 by means of a pressure piston 74 is also provided in this section upstream of entry port 54 (cf. FIGS. 4 and 9). By varying the length of this closed section of sealing element 70, said section being upstream of entry port 54, a precompression of the fluid still remaining in cylinders 16 can be realized and adjusted in that this section of sealing element 70 already covers fluid change openings 42, before the associated pistons 18 have reached their TDC.

(27) Furthermore, a pressure piston 74 is provided immediately behind (with respect to direction of rotation 72) entry port 54 and is followed by multiple further pressure pistons 74. It is provided that, on the one hand, the surfaces of the upper sides of pressure pistons 74, which are exposed to the inlet pressure of the fluid, are formed as increasing in direction of rotation 72 and, on the other hand, the distances between pressure pistons 74 are formed as decreasing in the direction of rotation, as a result of which a particular strong pressing of sealing element 70 against cylinder head plate 40 in a region comprising entry port 54 is achieved, whereas the contact pressure becomes smaller with increasing distance from entry port 54, whereby the contact forces generated by the individual pressure pistons 74 and acting on different regions of sealing element 70 are adapted to the fluid pressure progressively decreasing during the working cycles in cylinders 16.

(28) In order to prevent swash plate 22 from being carried along by the rotational movement of swash plate arm 24, it is provided to connect it, secured against rotation, to cylinder housing 12. A safety sleeve 82 is provided for this purpose, which is connected to cylinder housing 12. Safety sleeve 82 is also connected to swash plate 22 via a cardan-like joint assembly. The joint assembly connects swash plate 22 nonrotatably to safety sleeve 82 and thus to cylinder housing 12 and at the same time allows the wobbling movement of swash plate 22. The joint assembly comprises a joint ring 84, which is connected, rotatable about a first axis, to safety sleeve 82 via two bearing pins 86 each and to swash plate 22, rotatable about a second axis perpendicular to the first axis.

(29) Axial piston motor 10 can be used, for example, in a cyclic process device 88 for utilizing the waste heat of an engine 90 of an internal combustion engine of a motor vehicle (cf. FIG. 10). In this process, a vaporized, superheated, and pressurized fluid expands in axial piston motor 10, whereby a portion of the thermal and potential energy of the fluid is converted into mechanical energy or power (P.sub.mech). For this purpose, the fluid is conveyed in the liquid state by means of a pump 92 (conveying device) to an evaporator 94 in which it is heated by the transfer of thermal energy from the exhaust gas discharged from engine 90 via exhaust gas line integrating evaporator 94. The thus vaporized and superheated fluid then flows to axial piston motor 10 serving as the expansion device of the cyclic process device and from there in an expanded state to a condenser 34 of cyclic process device 88. In condenser 34, the fluid is cooled by a heat transfer to a cooling medium, for example, to a coolant flowing in a motor vehicle cooling system also integrating engine 90. In this case, the fluid condenses, so that it can again be supplied to evaporator 94 in the liquid state by means of pump 92. Due to the conveyance of the liquid fluid by means of pump 92, compression of the fluid, present in the gaseous state between evaporator 94 and axial piston motor 10 (expansion device), to an intended operating pressure is also achieved, wherein the pressure generation by means of pump 92 interacts with the expansion of the gaseous fluid in axial piston motor 10.

(30) Due to the work of pump 92, the pressure level is approached (theoretically) adiabatically and isentropically to a specified value according to the T-s diagram of FIG. 11 and a defined volume flow is ensured. A (theoretically) isobaric heat supply with evaporation and superheating takes place from state point b to state point c. Starting at state point b, evaporation begins, which is completed when state point b is reached. The vaporous fluid is superheated from state point b to state point c. The output of mechanical work (P.sub.mech) by axial piston motor 10 (expansion device) takes place by a (theoretically) isentropic expansion from state point c to state point d. Depending on the type and structure of the expansion device, expansion is now possible until just before the vapor region or into the wet vapor region. From state point d to state point a, the fluid is (theoretically) isobarically and isothermally liquefied by the condenser.

(31) The aim of the approach in the T-s diagram is a maximization of the supplied heat from state point b to state point c and a reduction of the heat (q_out) to be removed from state point d to state point a. The enclosed area from state point a via state points b and c to state point d should be maximized in the intended temperature range. The efficiency of a Clausius-Rankine process can thus be interpreted visually as the ratio of both areas (.sub.th=1(q_out)/(q_in)).

(32) The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are to be included within the scope of the following claims.