CYLINDER ASSEMBLY OF AN ORC ENGINE

Description

[0001] The invention relates to a cylinder assembly of an ORC engine with a crosshead for the articulated connection of a piston rod of a piston guided in a working cylinder to a connecting rod of the ORC engine, wherein the crosshead is movable in a guide in the longitudinal direction of the piston rod.

[0002] Known ORC engines with such an assembly are based on internal combustion engines whose cylinder liners serve to guide the crosshead. The working cylinder, which guides the piston, is directly connected coaxially to a cylinder liner of the internal combustion engine. Disassembly of the working cylinder and the assembly formed by the piston, piston rod, and crosshead, which is necessary for repair and maintenance work, is associated with considerable effort, particularly with the additional disassembly of the internal combustion engine's cylinder liners.

[0003] From the prior art, a cylinder assembly according to the preamble of claim 1 is known from NL 30 562 C. Further cylinder assemblies are known from US 2012 / 324889 A1 and from GB 119 157 A.

[0004] Different designs of crossheads are known from DE 12 64 882 B, from WO 2015 / 063031 A1, and from DE 20 2015 000722 U1.

[0005] The invention is based on the object of reducing the cost of repair or maintenance work on a cylinder assembly.

[0006] The present invention provides a novel cylinder assembly of the type mentioned above which is easy to assemble and is characterized in that the crosshead can be detached from the connecting rod in the direction of the working cylinder without complete or partial disassembly of the guide.

[0007] According to the invention, the guide leaves sufficient space for disassembly of the crosshead by axially displacing a connecting rod pin, and / or according to the invention, the crosshead can be disassembled into parts for disassembly from the connecting rod. Compared to the diameter of a bush-shaped guide, the crosshead is so small that the connecting rod pin connecting the crosshead and the connecting rod can be pushed laterally far enough out of its pivot bearings. According to one embodiment, the crosshead is formed from at least two half-shells enclosing the connecting rod pins connecting the crosshead and the connecting rod.

[0008] By detaching the crosshead from the connecting rod, a structural unit comprising the crosshead, the piston rod and the piston can be decoupled in its entirety from the connecting rod.

[0009] In a preferred embodiment of the invention, the crosshead comprises fork legs which have through openings for the connecting rod bolt and between which the free end of the connecting rod is arranged.

[0010] Preferably, the crosshead is secured against rotation around the longitudinal axis of the piston rod by the guide. This advantageously allows for the absorption of torques exerted on the aforementioned assembly during assembly work.

[0011] The guide preferably comprises a guide bushing coaxial with the longitudinal axis of the piston rod, with guide rails protruding from the inner wall of the bushing. The guide rails can, for example, form pairs of diametrically opposed guide surfaces, particularly flat guide surfaces, for the crosshead.

[0012] In particular, the fork legs protrude from a preferably conical section of the crosshead that can be connected to the piston rod. The conical shape of the crosshead ensures even transmission and distribution of the piston force via the piston rod to the fork legs.

[0013] In a particularly preferred embodiment of the invention, a detachable connection, in particular a screw connection, exists between at least one of the fork legs and the section. The crosshead can thus be disassembled into parts, making it possible to disassemble it even with limited movement of the connecting rod pin.

[0014] In a further embodiment of the invention, the piston rod is designed as a hollow body.

[0015] Preferably, the crosshead can be screwed to the piston rod and the piston rod to the piston via threads coaxial with the longitudinal axis of the piston rod.

[0016] Preferably, the thread diameter of the screw connection between the piston rod and the crosshead is larger than the thread diameter of the screw connection between the piston rod and the piston. This allows the piston to be detached from the piston rod separately, without loosening the screw connection between the piston rod and the crosshead.

[0017] In a further embodiment of the invention, a dowel pin connection is provided in addition to the aforementioned screw connections. This dowel pin connection ensures that the piston always assumes the same rotational position relative to the crosshead.

[0018] The invention will be further explained below with reference to exemplary embodiments and the accompanying drawings relating to one of these exemplary embodiments. They show: Fig. 1 shows a crosshead assembly of an ORC engine according to the invention in a sectional side view, and Fig. 2 shows a sectional plan view of the assembly of Fig. 1 .

[0019] One in Fig. 1 The assembly 1 of an ORC engine shown comprises a working cylinder 2, in which a piston 3 and a piston rod 4 rigidly connected to the piston 3 are guided. From a cylinder head (not shown) closing the working cylinder 2, a pin-like element 5 protrudes centrally towards the piston 3 for actuating an inlet valve for a pressurized working medium, which is accommodated in the cylinder head.

[0020] At its end facing away from the piston 3, the piston rod 4 is connected to a crosshead 6, which is guided within a bushing 7 coaxial with the working cylinder 2 in a direction parallel to the longitudinal direction of the piston rod 4 and is in turn connected to a connecting rod 8 moving the crosshead 6.

[0021] In the embodiment shown, the bushing 7 is a cylinder bushing of an internal combustion engine, which forms a basis for the ORC engine, wherein the working cylinder 1 and the structural unit of the ORC engine forming the piston 3, the piston rod 4 and the crosshead 6 take the place of the piston and the cylinder head of the internal combustion engine.

[0022] The articulated connection of the connecting rod 8 with the crosshead 6 is provided by a connecting rod pin 9, which is rotatably mounted in a bearing bush insert 10 of the connecting rod 8.

[0023] How Fig. 1 As can also be seen, the connecting rod pin 9 projects with its two ends into a bearing bush insert 11 or 12, wherein the bearing bush inserts 11, 12 are each arranged in a through-opening of a fork leg 13 or 14 of the crosshead 6. The connecting rod pin 9 is axially fixed in the bush inserts 10 to 12 by a boundary wall 15 in the opening of the fork leg 14 and a snap ring 16 accommodated in a groove in the opening of the fork leg 13.

[0024] How Fig. 1 As can also be seen, the crosshead 6 comprises a conical section 17, which merges integrally into the fork leg 13. The fork leg 14 is connected by screws 18 and 18' ( Fig. 2 ) detachably connected to the conical section 17.

[0025] As from Fig. 2As can be seen, diametrically opposed guide rails 20 and 20' are mounted on the inner wall of the bushing 7, each having two spaced-apart flat guide surfaces 21 and 21', respectively. The crosshead 6 slides against these guide surfaces 21, 21' with corresponding flat contact surfaces 22 and 22', respectively.

[0026] It is understood that the crosshead is secured against rotation about the longitudinal axis of the piston rod 4 by its engagement with the four guide surfaces. Four guide pins 23, 23', 23" and 23‴ projecting from the crosshead 6 against the inner wall of the bushing 7, which slide on the inner surface of the bushing 7, fix the crosshead 6 in a direction parallel to the guide surfaces within the bushing 7.

[0027] On its side facing away from the connecting rod 8, the partially hollow conical section 17 is connected to the piston rod 4 via an intermediate piece 24. A screw 25 connects the conical section 17 to the intermediate piece 24. An end section 26 of the intermediate piece 24 has an external thread that is screwed to an internal thread of the piston rod 4, which is designed as a hollow body.

[0028] Deviating from the example shown, the intermediate piece 24 could also be formed integrally with the conical section 17 or the piston rod 4.

[0029] The piston 3, which is provided with a guide ring 19, can be screwed to the piston rod 4 by means of a central screw 27.

[0030] It is understood that the sleeve 7 is connected to a crankcase (not shown) and the working cylinder 2 is connected coaxially to the bushing 7 to a cylinder bank (not shown) which may have several such bushings 7.

[0031] In the event of repair or maintenance work, after removing the working cylinder 2, the complete assembly consisting of the piston 3, the piston rod 4, and the crosshead 6 can be disassembled by loosening the connection between the crosshead 6 and the connecting rod 8 as follows: First, the snap ring 16 is removed using a tool inserted into the bushing 7. Due to the free space between the relevant pin end and the inner wall of the bushing 7, the connecting rod pin 9 can then be axially displaced until the other pin end of the connecting rod pin 9 no longer engages the bearing bush section 12. In the next disassembly step, the screws 18 and 18' are loosened and the fork leg 14 is removed.After axial displacement of the connecting rod pin 9 in the opposite direction until the engagement of the connecting rod pin 9 in the bearing bush insert 11 of the fork leg 13 is removed, the said structural unit can be decoupled from the connecting rod 8 in the direction of the axis of the bush 7 towards the cylinder head.

[0032] The guide pins 23, 23', 23" and 23‴ leave sufficient space in the bushing 7 to carry out the above-mentioned assembly steps, so that they can remain in place during assembly. In the example shown, they are permanently pinned to the bushing 7.

[0033] It is understood that the guide surfaces 21, 21' formed by the guide rails 20, 20' do not allow rotation of the crosshead 6 about the axis of the bushing 7.

[0034] This guide, which absorbs torques around the bushing axis, enables easy separate disassembly of only the piston 3 when the assembly consisting of the piston 3, the piston rod 4 and the crosshead 6 is installed.

[0035] When the central screw 27 is loosened, the guide easily absorbs any torque that occurs.

[0036] An unintentional loosening of the screw connection of the piston rod 4 with the intermediate piece 24 when loosening the screw 27 is prevented by the fact that, due to the larger thread diameter, a higher torque is required to loosen the latter screw connection than is required to loosen the screw 27.

[0037] The actuating element 5 normally impacts the piston 3 near the top dead center of the piston 3, vertically in the center of the piston. Transverse forces resulting from deviations in the impact position and angle within tolerance limits are absorbed by the guidance of the above-mentioned assembly in the working cylinder 2 via the guide ring 19 and in the bushing 7 by the rails 20, 20' as well as the inner wall of the bushing 7, against which the guide pins 23, 23', 23", 23‴ rest.

[0038] Lateral forces can be amplified if the actuating element 5 impacts the piston 3 after assembly work at an offset relative to a depression formed by constant impact with the piston surface. During assembly work, care must therefore be taken to ensure that the piston returns to its previous rotational position after reassembly. The reproducibility of the rotational position can be ensured by pinning between the piston 3 and the piston rod 4, as well as between the piston rod 4 and the crosshead 6.

Claims

1. A cylinder assembly (1) of an OPC engine having a crosshead (6) for the articulated connection of a piston rod (4) of a piston (3), which is guided in a working cylinder (2), to a connecting rod (8) of the OPC engine, the crosshead (6) being movable in a bushing-shaped guide (7) in the longitudinal direction of the piston rod (4), characterized in that the crosshead (6) can be detached from the connecting rod (8) in the direction towards the working cylinder without complete or partial removal of the guide, wherein, with the detachment of the crosshead (6) from the connecting rod (8), a structural unit formed by the crosshead (6), the piston rod (4) and the piston (3) can be uncoupled in its entirety from the connecting rod (8), and wherein the guide leaves free space for dismantling the crosshead (6) with axial displacement of a connecting rod pin (9) connecting the crosshead (6) and the connecting rod (8), in that the crosshead (6) is so small in comparison to the diameter of the bushing-shaped guide (7) that the connecting rod pin (9) can be pushed laterally far enough out of its pivot bearings.

2. The cylinder assembly (1) according to Claim 1, characterized in that the crosshead (6) can be disassembled into parts (17, 13; 14) for the purpose of disassembly, in that the crosshead (6) is formed from at least two half-shells enclosing a connecting rod pin (9) connecting the crosshead (6) and the connecting rod (8).

3. The cylinder assembly (1) according to Claim 2 or 3, characterized in that the crosshead (6) comprises fork legs (13, 14) which have through-openings for the connecting rod pin (9) and between which the free end of the connecting rod (8) comes to be arranged.

4. The cylinder assembly (1) according to Claim 3, characterized in that the fork legs (13, 14) protrude from a section (17) of the crosshead (6) which is preferably conical and can be connected to the piston rod (4).

5. The cylinder assembly (1) according to Claim 4, characterized in that there is a detachable connection, in particular by means of screws (18, 18') between at least one of the fork legs (13, 14) and the conical section (17).

6. The cylinder assembly (1) according to any one of Claims 1 to 5, characterized in that the crosshead (6) is secured by the guide against rotation about the longitudinal axis of the piston rod (4).

7. The cylinder assembly (1) according to any one of Claims 1 to 6, characterized in that the guide has a guide bushing (7) which is coaxial to the longitudinal axis of the piston rod (4) and has guide rails (20, 20') protruding from the bushing inner wall.

8. The cylinder assembly (1) according to Claim 7, characterized in that the guide rails (20, 20') form diametrically opposed guide surfaces (21, 21'), optionally comprising, in particular, flat guide surfaces.

9. The cylinder assembly (1) according to any one of Claims 1 to 8, characterized in that the piston rod (4) is in the form of a hollow body.

10. The cylinder assembly (1) according to any one of Claims 1 to 9, characterized in that the crosshead (6) can be screw-fastened to the piston rod (4) and the piston rod (4) can be screw-fastened to the piston (3) via threads which are coaxial to the longitudinal axis of the piston rod (4).

11. The cylinder assembly (1) according to Claim 10, characterized in that the thread diameter of the screw-fastening of the piston rod (4) to the crosshead (4) is greater than the thread diameter of the screw-fastening of the piston rod (4) to the piston (3).

12. The cylinder assembly (1) according to Claim 10 or 11, characterized in that in each case a dowel pin connection is made in addition to the screw-fastenings.