EP0153982B1 - Piston machine, especially a piston pump - Google Patents

Description

The invention relates to a piston machine according to the preamble of claim 1. A machine of this type designed as a piston pump is known from DE-A-2 554 733.

Piston machines of the above type generally have a comparatively high space requirement with regard to the usable stroke volume, because the stroke deformation of the tubular sealing member may only make up a fraction of the hose length due to the material-related limitation of the permanent alternating deformation. The devices for supporting the elastically deformable sealing hose by means of pressure lubrication have a similar influence. There is therefore a particular need for this type of machine, due to its specific characteristics, to reduce the space required for the guiding and driving device of the piston-cylinder arrangement. In addition, the frictional heat that arises in the area of the sliding guide of the piston and the sealing hose should have a low temperature gradient, i.e. can be dissipated to the outside through large contact areas. In this regard, the above-mentioned arrangement of known type is in need of improvement.

From GB-A-650 312 a tappet-like design of a piston for a hydraulic pump is known, within which a helical spring for accommodating the piston against a drive eccentric is accommodated. A hose-like, elastically deformable sealing member is not available there. In this known arrangement, therefore, there is neither the problem of reducing the specific space requirement nor that of the removal of frictional heat from the area of a sealing element which is under internal pressure and, due to its elasticity, is under appropriate contact pressure against the guide surface.

The object of the invention is therefore to provide a piston engine or driven machine which is distinguished by a comparatively short overall length of the piston-cylinder arrangement, including the adjacent parts of the drive device. The inventive solution to this problem is characterized by the features specified in claim 1. The subsequent design, encompassing the cylinder, of the drive member, for example a ram or the like which is conventional per se and which cooperates with an eccentric drive device, makes it possible, with the same support and guide length, for this drive member, which oscillates in accordance with the working movement, to substantially shorten the overall length of the Piston-cylinder arrangement. The easily possible, thin-walled design of the portion of the drive member encompassing the cylinder makes it possible to avoid a substantial increase in the diameter of the piston-cylinder arrangement. The reduction in the overall length of the piston-cylinder arrangement is particularly noticeable in the case of star-shaped multi-cylinder arrangements, because this overall length reduces the overall diameter of the pump.

In the case of constructions of the present type, on the outside of the cylinder enclosed by the drive member, a pulsating secondary space results, corresponding to the oscillating working movement of the latter, which occurs in the case of conventional pistons with leakage liquid from the working space or in the case of hermetic sealing of the working space by means of the elastically deformable sealing hose with pressure lubrication support mentioned can fill the outflowing lubricant. In order to master the problems of liquid discharge resulting therefrom, an advantageous development of the invention provides at least one compensating channel with a large cross-section between the pulsating secondary space and a pressure equalizing space. As a result, pressure surges within the piston-cylinder arrangement are avoided in a simple manner and, in particular, flawless discharge of even larger lubricant throughput quantities is ensured. In this case, it is expedient to provide a lubricant or conveying means storage space (in view of the removal of circulating lubricant or leakage conveying means from the working space) as a pressure compensation space for the pulsating secondary space.

A development of the invention based on the aforementioned aspects provides that the pulsating secondary space is connected to a space located at the end of the cylinder within the drive member and pulsating in accordance with the oscillating working movement by a throttle channel. As a result of this design, the pulsating space between the cylinder end and the drive member, into which the lubricant or the leakage liquid flowing out of the cylinder or from the sealing hose collects from the work space, is used as a pump or auxiliary work space for the continuous discharge of the accumulating liquid, whereby the throttle channel limits the backflow of the liquid from the pressure-relieved adjoining room at the other end of the drive member to a small extent in a particularly simple manner. The throttle channel thus acts like a check valve.

Another development of the invention relates to a combination with features which, in a different context, belong to the subject matter of EP patent application No. 80103359.8, which has now been granted (EP-B-21315). Such a combination with the present invention features relates in particular to a circulating pressure lubrication, as can be used in particular for the lubrication and support of an elastically deformable sealing hose during its sliding movement on a support surface. For a machine with pressure lubrication, the one Pressure lubrication pump, a return collection chamber, a return pump and a supply chamber feeding the pressure lubrication pump, this development of the invention is characterized by an overflow channel connecting the supply chamber to the return collection chamber with an adjustable or controllable actuator for limiting the flow from the supply chamber to the return line. Gathering room. This design enables a safe filling and thus a trouble-free operation of the return pump and thus the maintenance of the lubricant pressure, which is essential for the overall operational safety, in a simple manner. This is particularly important in the case of high-pressure pumps with a lubricated sealing hose because failure of the lubrication on the support surface can very quickly result in damage to the sealing hose.

• Fig. 1 einen Axialschnitt einer Kolbenpumpe mit sternförmiger Mehrzylinderanordnung mit Exzenterantrieb,
• Fig. 2 das Prinzipschaltbild des Schmiermittelsystems der Pumpe nach Fig. 1,
• Fig. 3 in grösserem Masstab eine Axialansicht einer Rücklaufpumpe des Schmiermittelsystems der Pumpe nach Fig. 1 und
• Fig. 4 einen Teilschnitt des Pumpenrades gemäss Fig. 3 entsprechend Schnittebene IV-IV,
• Fig. 5 einen Teil-Axialschnitt der Pumpe, ähnlich Fig. 1, jedoch mit abgewandeltem Bereich der Vorförderpumpe und des Schmiermittel-Vorratsraumes mit eingesetztem Wärmetauscher und
• Fig. 6 einen Querschnitt der Maschine im Bereich des Schmiermittel-Vorratsraumes mit Wärmetauscher, gemäss Schnittebene VI-VI in Fig. 5.

A further development of the invention relates to that known type of machine designed as a pump, in which a prefeed pump for the pressure supply of the working medium is provided on the inflow side of the pump. A particularly intensive heat exchange between the working fluid and the lubricant, and thus in turn the possibility of reducing the size of the cooling device, results according to the invention in that the working fluid inflow side of the heat exchanger is connected to the outflow side of the pre-feed pump. The pre-feed pump, which is present anyway, is thus used for a forced circulation of the cooling working fluid in the lubricant heat exchanger. A particularly advantageous embodiment results in this connection by designing the working medium system of the heat exchanger as a second return flow between the outflow side and the inflow side of the pre-feed pump. In order to keep the backflow of the working fluid within appropriate limits, a throttle, preferably an adjustable throttle, can be arranged in the heat exchanger backflow branch according to an expedient embodiment of the invention. In a different context, these features also belong to the subject of EP-A-80103359.8. Further features and advantages of the invention are explained on the basis of the exemplary embodiments illustrated in the drawings. Herein shows:

• 1 is an axial section of a piston pump with a star-shaped multi-cylinder arrangement with an eccentric drive,
• 2 shows the basic circuit diagram of the lubricant system of the pump according to FIG. 1,
• Fig. 3 on a larger scale an axial view of a return pump of the lubricant system of the pump according to Fig. 1 and
• 4 shows a partial section of the pump wheel according to FIG. 3 corresponding to section plane IV-IV,
• Fig. 5 is a partial axial section of the pump, similar to Fig. 1, but with a modified area of the pre-feed pump and the lubricant reservoir with the heat exchanger and
• 6 shows a cross section of the machine in the area of the lubricant storage space with a heat exchanger, according to section plane VI-VI in FIG. 5.

The drive device 10 of the pump according to FIG. 1 consists of a shaft 1 with an eccentric 2 coupled to a motor, not shown, on which a non-rotating, translationally rotating sliding piece 3 with a number of tangential pressure surfaces 4 corresponding to the number of cylinders - here for example five - is mounted . In Fig. 1, such a pressure surface is indicated in operative connection with a drive member 30 of a piston 20 which is connected to an elastically deformable sealing hose 22. A coil spring 23 presses the piston 20 against the bottom portion 30b of the sleeve-shaped drive member 30 and sets the sealing hose under axial tension. The sealing hose sits in the bore of a cylinder 25, with which it is firmly connected at the upper end, and thus hermetically seals the working space 24 formed in the hose interior. This working space changes its volume in accordance with the oscillating movement of the drive member 30 and generates the pumping action in connection with check valves 26 and 27, which are connected to a delivery and suction channel 28.

The lubrication system of the pump is in the form of pressure circulation lubrication with a gear pressure lubrication pump 100, a return collecting space 120 surrounding the eccentric 3 of the drive device and with an annular storage space 110 concentrically surrounding the axis of rotation XX of the drive device and with one from the return collecting space 120 into the Storage pump 110 promoting return pump 105 is formed. This design and arrangement of the storage space enables a particularly space-saving multi-cylinder pump construction with a symmetrical distribution of the connections to the individual cylinders over the circumference of the ring. The inclusion of the storage space in the cylindrical housing of the star-shaped multi-cylinder arrangement also serves the same purpose.

The pressure lubrication pump 100 delivers from the storage space 110 via channels 103 and 104 and a filter 102 into an annular distributor channel 101, from where pressure channels 90 and 95 lead to the individual cylinders 25 with adjusting throttles 90a and 95a. The pressurized lubricant from the channel 90 is supplied to support the sliding movement of the outer surface of the sealing hose 22 and flows in the axial direction of the cylinder (downwards according to FIG. 1) into a pulsating space 42 formed in the area of the lower piston and cylinder end . This space stands over a throttle channel 45, which is designed as a gap space between the inner surface of the cylindrical section 30a of the drive member 30 and the outside of the cylinder 25, with a formed at the upper end of the cylindrical section 30a, also pulsating adjoining room 35 in connection. In this way, the relaxed lubricant flowing out in the space 42 is conveyed via the throttle channel 45, which acts as a quasi check valve, into the adjoining space 35, so that the space 42 essentially acts as a low-pressure space for an undisturbed outflow of the lubricant from the gap between the sealing hose and the cylinder bore or support surface acts. For this automatic discharge pumping action, low pressure is also required in the adjoining room 35. For this purpose, the latter is connected to the storage space 110 via a compensation channel 40 with a large cross section, which thus serves as a pressure compensation space.

The lubricant supplied via the channel 95 reaches the outer surface of the cylindrical section 30a of the drive member 30, where the latter is guided so as to be displaceable coaxially with the cylinder 25. The lubricant then flows via lubrication channels 47 to the pressure surfaces 4 and further into the return collecting space 120. This lubricant circuit is thus also closed.

The return pump 105 draws in via a duct 115 from the lower part of the collecting space 120 and delivers via an ascending return duct 106 in the apex region 110a of the storage space 110. This results in an effective ventilation of the lubricant flow entering the storage space. For safe filling of the return pump, the suction space of the latter, i.e. the lower part of the collecting space 120, with the storage space 110 connecting overflow channel 130 is provided, which prevents this area from being sucked empty. An actuator is provided for limiting the overflow, for which an adjustable throttle 135a may be sufficient, for example. In the example, on the other hand, an overflow control with a controllable valve 135 as an actuator and with a float 140 as a control device is provided. This allows the maintenance of an optimal filling level in the suction space of the return pump 105. The sufficient filling of the return pump is particularly important also for the avoidance of foam formation, which would impair a reliable pressure circulation lubrication.

The pressure circulation lubrication system of the pump is shown schematically in a clear form in FIG. 2, the essential functional elements being shown symbolically, but with the same reference numerals as in FIG. 1.

As already mentioned, the avoidance of foam formation in the delivery system of the circulating pressure lubrication is essential for a perfect function. This is particularly useful for the design of the rotor 105a of the return pump 105 shown in FIGS. 3 and 4 with a plurality of slots designed as storage spaces 105b, which are arranged in the manner of a radial centrifugal pump and extend over a radius difference with respect to the axis of rotation XX of the pump . As a result of the strong centrifugal forces, the lubricant in these storage spaces is subject to a separation between lubricant with a greater or lesser liquid content or, conversely, a lower and greater gas or foam content. In the region of an outflow control opening 108 which extends over less than 180 °, with a suitable slowdown or throttling of the outflow from the pump, essentially only that part of the lubricant which has only a very low gas or foam content is expelled radially from the storage spaces 105b. The stowage spaces then come into connection with an outflow control opening 109b which receives the gas or foam-rich part of the lubricant and leads back into the collecting space 120 via an outflow channel 109c, which is not shown in detail. In the area between the outflow control openings 108 and 109b, which, as shown in FIG. 3, likewise extend over an angle of substantially less than 180 °, the storage spaces 105b are closed at their outer ends by a housing inner surface 107, so that this Part of the circulation is available for separating the differently dense lubricant components without disturbance due to flow.

Another mechanism that contributes to gas and foam cut-off within the rotor of the return pump is indicated in FIG. 4. Thereafter, a radial circular flow with a course indicated at A can be generated by means of a comparatively wide gap space 109a arranged axially next to the rotor 105a, which is shown here in a strongly distorting manner, which prevents the gas-poor lubricant from accumulating in the radially outer regions of the storage spaces 105b favored and possibly also a partial return of the foam accumulated in the radially inner storage space areas in the direction of the suction space of the pump.

It should be mentioned in particular that the compact design of the pump shown in FIG. 1 is further favored by the fact that a pre-feed pump 150 for the working medium of the pump is also accommodated within the annular lubricant storage space 110 arranged at the end to the cylinders 25.

In the pump embodiment shown in FIGS. 5 and 6, a cooling device for the lubricant, designated overall by 200, is accommodated within the annular lubricant storage space 110. This cooling device essentially consists of a heat exchanger 210 which has a channel system 212 through which the working medium of the pump flows and which can be seen in detail in FIG. 6. The flow of the working medium in this channel system is achieved by means of the feed pump 150 already mentioned, which is accommodated coaxially to the annular storage space 110 and with an axial overlap in its inner recess space 140. The inflow side 160 of the pre-conveyor Pump 150 lies in the area of an axial end cover 155 of the pump housing, which is aligned with an end wall 230 closing off the storage space 110. In the example, the prefeed pump is designed as an axial flow pump, the rotor of which is seated on the pump shaft 1 in the manner shown schematically in FIG. 5 and the outflow side 170 of which is connected to an annular channel 174 by radial channels 172. From the latter, axial branch ducts 176 (only one of these ducts is shown in FIG. 5) lead to the individual, pump-shaped pump cylinders (not shown in detail). In this way, the piston-cylinder arrangements of the pump receive the working fluid with a pre-pressure of, for example, a few atmospheres, which is sufficient for a safe filling in the suction stroke of the pistons.

Channel sections 178 which are lengthened at the rear connect the outflow side 170 of the pre-feed pump 150 to an annular channel 180 in a central, section-like section 232 of the end wall 230. From the ring channel 180, a radial channel 182 leads to an inflow distributor 216 of the heat exchanger which is inserted in the outer part of the end wall 230 210. From this inflow distributor arranged in the lower apex area of the storage space 110, the partial flow of the cool working medium branched off from the outflow side of the pre-feed pump passes via a channel system 212 of the heat exchanger 210, which can be seen in detail in FIG. 6, to one in the upper apex area of the storage space 110, ie Outflow collector 218 arranged diametrically to the inflow distributor 216. The latter is also inserted into the outer part of the end wall 230. The outflow collector is connected to the suction side 160 of the prefeed pump via a radial channel 184. This results in a return flow circuit parallel to the main delivery flow for the branched-off part of the delivery flow of the prefeed pump 150, which is fed to the inflow side of the main pump. In order to be able to adjust the bridging and the pressure conditions at the pre-feed pump 150 appropriately, taking into account the return flow circuit, a throttle screw 220 is inserted into the end wall 230, the tip of which engages in the channel 182 and here forms an adjustable throttle point in the partial feed flow to the inflow distributor 216.

The design of the heat exchanger can be seen in detail in FIG. 6. The channel system 212 of the heat exchanger is then practically completely submerged within the lubricant storage space 110 and below the lubricant level. As a result of the confluence of the return flow channel 106 from the lubricant return pump 105 in the upper apex area 110a of the storage space 110 and the suction by the pressure lubrication pump 100 in the lower apex area, a lubricant flow results in the annular storage area, which flows downward in essentially both circumferential directions from the upper apex area lower apex runs. This flow is obviously directed in the opposite direction to the working medium flow in the channel system of the heat exchanger 210 between the lower inflow distributor 216 and the upper outflow collector 218. So there is a countercurrent heat transfer between the lubricant throughput in the storage space 110 on the one hand and the working fluid flow in the channel system of the heat exchanger 210 and thus an intensive cooling of the lubricant by the freshly entering working fluid.

The following applies in detail to the construction of the heat exchanger with reference to FIG. 6: The channel system 212 of the heat exchanger 210 comprises a plurality of ring-shaped heat exchanger tubes 214 which extend in the circumferential direction of the storage space 110 and which, as mentioned, essentially below the lubricant level and therefore enable heat exchange over their entire surface. On both sides of the inflow distributor 216 and the outflow collector 218, a plurality of heat exchanger tubes 214 connected in parallel, arcuate and adapted to the ring shape of the storage space 110 are connected. The result is an essentially cylindrical arrangement of heat exchanger tubes lying side by side in the cylinder axis direction, i.e. a large-scale arrangement of heat transfer surfaces adapted to the spatial conditions of the storage space and the lubricant flow.

Obviously, there is no additional space requirement for this intensely acting heat exchange arrangement, because the entire arrangement is housed within the lubricant storage space which is already present. The annular design of the latter space not only enables space-saving inclusion in the overall construction of the machine housing, but also forces a lubricant flow in the circumferential direction of the storage space along the heat exchanger tubes in the sense of counterflow cooling.

Claims (11)

1. A hydraulic piston machine comprising at least one piston-cylinder arrangement (20, 25) forming a pulsatory working space (24), wherein for the purpose of sealing the pulsatory working space being filled with a liquid said piston-cylinder arrangement comprises a tubular, flexibly deformable sealing member (22), which is solidly connected on one side with the cylinder (25) and on the other side with the piston (20) and which is supported on the tube circumference via a lubricant by a supporting surface provided at the housing, characterized in that provision has been made for an eccentrically rotating drive device (10) being in operating connection with the piston (20), and in that a bushing shaped drive member (30) is assigned to each piston-cylinder arrangement (20, 25), said drive member surrounding said cylinder (25) on at least part of the cylinder length, and a bottom portion (30b) of said drive member (30) being connected at its inner surface with said piston (20) and being supported on its outer surface by a bearing surface (4) of said drive device (10).

2. A piston machine according to claim 1, characterized in that an auxiliary space (35) is formed by said drive member (30) at the outer side of the cylinder (25), said auxiliary space pulsating according to the oscillating operation movement of the drive member and being connected through at least one release channel (40) of comparatively great cross-section with a pressure release space (110).

3. A piston machine according to claim 2, characterized in that said pulsating auxiliary space (35) is connected via a throttling channel (45) to a space (42), which is pulsating according to the operation movement and located within said drive member (30) at the end (25a) of said cylinder.

4. A piston machine according to claim 3, characterized in that said throttling channel (45) is formed by a clearance between the inner surface of said drive member (30) and the outer surface of said cylinder (25).

5. A piston machine according to any one of claims 2 to 4, characterized in that a storage space for a lubricant or pumping medium is provided as said pressure release space (110) for the pulsating auxiliary space (35).

6. A piston machine according to any one of the preceding claims, characterized in that a pressure circulating lubrication is provided, comprising a pressure lubricating pump (100), a runback collecting space (120), a runback pump (105) and a lubricant storage space (110) feeding said pressure lubricating pump, and in that said lubricant storage space (110) is connected to the runback collecting space (120) via an overflow channel (130).

7. A piston machine according to claim 6, characterized by an overflow channel (130) provided with a controlling or adjusting member (135) for limiting the flow from said storage space (110) to the runback collecting space (120).

8. A piston machine according to claim 7, characterized in that a control or adjustment device (140) maintaining a minimum filling ratio is provided for said runback collecting space (120), and in that said control or adjustment device (140) is operationally connected with said flow controlling or adjusting member (135) in said overflow channel (130).

9. A piston machine according to any one of the preceding claims, characterized in that provision is made for a rotating drive device (10) establishing said pulsating working space and for a pressure circulating lubrication comprising a storage or collecting space (110) connected with a lubricant runback, and in that said storage or collecting space (110) is of annular shape and surrounding the rotational axis (XX) of said drive device (10) and preferably is arranged concentrically in relation to said axis.

10. A piston machine according to claim 9, characterized in that the medium annular plane of said storage or collecting space (110) is substantially vertical, and in that provision is made for a runback pumping channel (106) connected to the runback pump (105), said runback pumping channel leading into the range of the summit (110a) of said annular storage or collecting space.

11. A piston machine according to claim 9 or 10, characterized in that provision is made for a star-shaped multiple cylinder arrangement, and in that said storage or collecting space (110) is arranged coaxially to and on the face of said star-shaped multiple-cylinder arrangement and in a common housing therewith.

Images