Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H57/00—General details of gearing
  • F16H57/04—Features relating to lubrication or cooling or heating
  • F16H57/048—Type of gearings to be lubricated, cooled or heated
  • F16H57/0482—Gearings with gears having orbital motion
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
  • F16H—GEARING
  • F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
  • F16H55/02—Toothed members; Worms
  • F16H55/06—Use of materials; Use of treatments of toothed members or worms to affect their intrinsic material properties

Definitions

• Hydraulic machine having at least one of its gearwheels made of a friction-reducing plastics material.
• the invention relates to a gear for a hydraulic piston machine, having at least one gear pairing comprising two gearwheels.
• Gears are generally used to convert the output speed of a hydraulic machine so that a specific speed or a specific speed range i ⁇ achieved. In this connection it is desirable for the gear to have as long a service life as possible and to cause as few losses as possible. For that reason, gears are normally lubricated, grease or oil frequently being used for that purpose.
• the hydraulic oils used in the past have the advantage, however, that they serve not only as the hydraulic medium but at the same time have lubricating properties which reduce friction between moving parts of the hydraulic machine, and are compatible with the lubricant used for the gear.
• US 5 038 523 discloses a motor-driven tool which for underwater use can be operated with sea-water as the hydraulic fluid.
• an angular gear is provided, which comprises two bevel gears made of a plastics material, namely, Delrin. But because of the limited strength of the plastics material, the torques that can be transmitted with such a gear are restricted. In many cases these transmission properties are inadequate.
• the invention is based on the problem of constructing a gear so that it is also able to transmit relatively high forces from a hydraulic machine that is operated with a fluid that has no or only slight lubricating properties, in particular from a machine that is operated with water as the hydraulic fluid.
• That problem is solved in a gear of the kind mentioned at the outset in that the first of the two gearwheels is made of a metal and the second of the two gearwheels consists, at least at its ⁇ urface, of a friction- reducing plastics material.
• Combining the metal with the plastics materials results, on the one hand, in low-friction co-operation of these two parts so that lubrication or cooling to the extent previously required is not necessary. On the contrary, lubrication or cooling is taken over by the plastics material in co-operation with the fluid. Moreover, combining the metal with the plastics material also has the advantage that improved strength of the gearwheel pairing is achieved.
• One of the two gearwheel ⁇ , to be preci ⁇ e, the metal one has the same strength as before, that is, as in a conventional gear comprising gearwheels that all consist of metal.
• the second gearwheel having the plastics material has a somewhat lower strength, but in co-operation with the metal gearwheel it fulfils its function satisfactorily.
• the second gearwheel advantageously consists entirely of the plastics material. This facilitates manufacture. The risk that a plastics material will become detached from a core, for example, a metal core, no longer exists.
• the pla ⁇ tics material prefferably be fibre-reinforced, in particular with glas ⁇ fibre ⁇ and/or carbon fibres and/or organic fibres. Reinforcement with glas ⁇ fibre ⁇ or carbon fibre ⁇ increa ⁇ e ⁇ the strength of the pla ⁇ tic ⁇ material quite con ⁇ iderably, ⁇ o that part ⁇ that can be loaded to the de ⁇ ired extent are obtained.
• the plastics material has a tensile strength of more than 200 N/mm 2 .
• plastics materials having friction-reducing properties which have this tensile strength.
• the plastics is selected from the group of high-strength thermoplastic plastics materials based on polyarylether ketones, in particular polyether ether ketones, polyamides, polyacetals, polyaryl ethers, polyethylene terephthalates, polyphenylene sulphide ⁇ , poly ⁇ ulphones, polyether sulphones, polyether imides, polyamideimide, polyacrylates, phenol resins, such a ⁇ novolak resins, or similar substances; glas ⁇ , graphite, polytetrafluoroethylene or carbon, especially in fibre form, can be used a ⁇ fillers. Water can be used as the hydraulic fluid when such materials are used. Polyetherether ketones (PEEK) have proved especially suitable, because this plastics material has only a very slight absorptive capacity for water.
• PEEK Polyetherether ketones
• the first gearwheel preferably has a smaller diameter than the second gearwheel.
• the ⁇ maller one i ⁇ made of metal The smaller gearwheel generally has to absorb the larger forces or moments. But since the metal gearwheel will generally have a greater strength than the plastics gearwheel this property is meaningfully exploited in thi ⁇ combination.
• the first gearwheel is held by at least three second gearwheels distributed circumferentially.
• the fir ⁇ t gearwheel therefore has a rotary bearing which manages without a bearing axle or a journal. No friction is generated in that case between the fir ⁇ t gearwheel and its journal.
• friction forces do occur between the individual gearwheel ⁇ , in particular at the tooth flank ⁇ , thi ⁇ i ⁇ acceptable because, firstly, in these gearwheels the co-operating material pairing is always a metal/plastics material pairing.
• each tooth is only briefly affected by friction. When this tooth has passed through its contact point with the other tooth, it is free again and is able to cool down.
• the "journal-free" mounting of the first gearwheel therefore contributes to the reduction in friction losses.
• the ⁇ econd gearwheel i ⁇ rotatably mounted on a journal, a groove being formed between the gearwheel and the journal.
• the journal con ⁇ i ⁇ ts of metal, the material pairing in this case i ⁇ again metal/pla ⁇ tic ⁇ .
• the ⁇ e two aterial ⁇ work together with little friction.
• friction lo ⁇ ses cannot be completely avoided here.
• the groove between the gearwheel and the journal therefore serve ⁇ to allow fluid to penetrate into the region between gearwheel and journal. Thi ⁇ fluid can then ea ⁇ ily di ⁇ ipate the heat caused by friction. The friction then has no adverse effects on the service life of the gear.
• the groove which can also be referred to as a channel, can be provided on the circumferential surface of the journal or alternatively in the inner ⁇ urface of the gearwheel that surrounds the journal.
• a channel can be provided on the circumferential surface of the journal or alternatively in the inner ⁇ urface of the gearwheel that surrounds the journal.
• the groove is here especially preferred for the groove to run helically. As the gearwheel rotates on the journal, a kind of pumping effect then occur ⁇ , by which the fluid i ⁇ conveyed into the region between the gearwheel and the journal.
• the second gearwheel it i ⁇ especially advantageous for the second gearwheel to have at lea ⁇ t one channel running circumferentially.
• the channel interrupts the teeth for a part of their axial length, but this has the advantage that fluid i ⁇ able to enter the gaps between the teeth more ea ⁇ ily, to be precise, into the region in which the second gearwheel me ⁇ he ⁇ with the first gearwheel. Any heat occurring can therefore be dis ⁇ ipated immediately and directly.
• It i ⁇ especially preferred for the channel to have a depth corresponding to the depth of the teeth. Even in the regions in which the two gearwheels engage with one another, a permanent exchange of fluid that is not hampered by the engagement is then pos ⁇ ible.
• the second gearwheel is in that ca ⁇ e preferably formed from two gearwheel parts which are ⁇ eparated from one another by a spacer washer.
• the two gearwheel parts and the spacer washer then lie axially on top of each other. Such a procedure facilitates manufacture.
• the internal diameter of the second gearwheel is enlarged at the end face in the region of the journal. Such an enlargement facilitates pressure equalization across the gearwheel. Occasionally, differences in pressure are unavoidable. The risk that these difference ⁇ in pre ⁇ sure will lead to uneven loading and thus to an increa ⁇ e in the friction of the ⁇ econd gearwheel on it ⁇ journal thus becomes less.
• the gearwheels are arranged in a hou ⁇ ing which i ⁇ filled with water.
• Water may have no or only slight lubricating propertie ⁇ , but it doe ⁇ serve to dis ⁇ ipate heat that occurs from the places affected by friction. With appropriate dimensions, this water cooling is ⁇ ufficient to ensure a sati ⁇ factory operation combined with an acceptable ⁇ ervice life.
• the water is al ⁇ o able to flow through the gear.
• the gearwheels can be in direct contact with the water.
• the gear is connected to a connection for leakage fluid of the hydraulic machine.
• a connection for leakage fluid of the hydraulic machine With mo ⁇ t machine ⁇ it i ⁇ virtually impo ⁇ ible to prevent the e ⁇ cape of a certain amount of leakage fluid.
• the water ⁇ erve ⁇ a ⁇ hydraulic fluid In the hydraulic machine the water ⁇ erve ⁇ a ⁇ hydraulic fluid.
• the first gearwheel i ⁇ provided on one end face with a layer of friction-reducing pla ⁇ tic ⁇ material.
• Thi ⁇ layer does not change the strength of the first gearwheel. It does, however, allow the first gearwheel to be ⁇ upported axially to a certain extent.
• a planetary gear favourable transmission ratios can be achieved with a small overall size.
• the second gearwheels in the planet wheel carrier are then virtually the only gearwheel ⁇ that have to be journalled in order to be able to rotate.
• the fir ⁇ t gearwheel i ⁇ held by the ⁇ econd gearwheel ⁇ in the planet wheel carrier.
• the only frictional engagement to take place is then between the first and the second gearwheels through the metal/plastics material pairing.
• the second gearwheels can rotate freely on the planet wheel carrier because they are mounted therein likewise with a plastics material/metal combination.
• the second gearwheels in the planet wheel carrier in turn co-operate with an internally toothed ring.
• This toothed ring can also be made of metal.
• the first gearwheel can consist of steel, especially stainless steel.
• the toothed ring can consist of the same or a different metal, for example, it can al ⁇ o consist of aluminium.
• Fig. 1 is a plan view of an opened gear and Fig. 2 is a longitudinal section through a gear assembled with a radial piston motor.
• Fig. 1 show ⁇ a plan view onto an open gear 1, which i ⁇ illu ⁇ trated in Fig. 2 coupled up to a motor 2.
• the motor i ⁇ here in the form of a radial piston motor known per se. Explanation thereof is therefore unnecessary.
• the view according to Fig. 1 is obtained when the motor 2 is removed from the gear 1 and the observer looks from the right (in Fig. 2) at the gear.
• an axial pi ⁇ ton motor can be used.
• the gear 1 has a housing 3 in which a toothed ring 4 having an internal toothing 5 is non-rotatably mounted.
• a gearwheel 6 which shall be referred to hereinafter as the first gearwheel and ha ⁇ the function of a sun wheel in the gear 1.
• the first gearwheel 6 has an external toothing 7 and an internal toothing 8, the latter meshing with a complementary external toothing of a driven shaft 9 of the motor 2.
• the fir ⁇ t gearwheel 6 is therefore non-rotatably connected to the driven shaft 9. Certain axial displacement ⁇ are allowed, however.
• a ⁇ second gearwheels 10 are arranged on a common carrier 11 and have the function of planet wheels.
• the number of teeth or the diameter of the first and second gearwheels 6, 10 and of the toothed ring 4 determine the transmi ⁇ sion ratio of the gear.
• the carrier 11 For mounting the second gearwheels 10, the carrier 11 has a respective journal 12 for each second gearwheel 10, on which the ⁇ econd gearwheel 10 i ⁇ able to rotate.
• the second gearwheel 10 is ⁇ ecured on its journal 12 by mean of a spring ring 13. With its other side the gearwheel 10 lies against the carrier 11, if desired, through the intermediary of a bearing washer 14.
• a helical circumferential groove or channel 15 is provided on the journal 12, or more accurately, in a circumferential surface; thi ⁇ groove is so arranged that it covers the entire region between the second gearwheel 10 and its journal 12 both circumferentially and axially.
• Thi ⁇ rece ⁇ 19 facilitate ⁇ , fir ⁇ tly, the entry of fluid into the circumferential helical groove 15.
• the rece ⁇ 19 al ⁇ o improves the opportunities for pres ⁇ ure equalization across the second gearwheel 12, so that there is less risk of skewing.
• the inside of the housing 3 is filled with fluid, in particular with water, so that on rotation of the second gearwheel 10 on the journal 12 the fluid is conveyed through the groove 15 and i ⁇ able to di ⁇ ipate any heat generated in the region between journal 12 and ⁇ econd gearwheel 10.
• the ⁇ econd gearwheel 10 consists of two gearwheel parts 10a, 10b which are separated from one another by a spacer washer 10b.
• a channel 16 is consequently formed circumferentially in the toothing of the second gearwheel 10; the channel 16 is at least as deep a ⁇ the teeth of the second gearwheel 10.
• the first gearwheel 6 consists of stainles ⁇ steel.
• the second gearwheels 10 consist of a plastics material, especially of polyether ether ketone (PEEK) .
• PEEK polyether ether ketone
• PEEK of the type 450CA30 can be used for that purpose, because this material has relatively high resistance to pressure and tensile strength. Its tensile strength i ⁇ more than 210 N/mm 2 .
• a ⁇ econd gearwheel 10 made of this material can therefore absorb a load that is about 90% of that of a ⁇ teel gearwheel. Such a load capability i ⁇ ⁇ ufficient, however.
• a ⁇ is especially clear from Fig. 1, the first gearwheel 6 has a smaller diameter than the second gearwheel ⁇ 10.
• the large ⁇ t force ⁇ therefore occur here, but can be ab ⁇ orbed without difficulty because the first gearwheel 6 consists of stainless steel.
• the load on the second gearwheels 10 i ⁇ di ⁇ tributed over three gearwheel ⁇ of larger diameter so that this loading is correspondingly smaller there.
• the first gearwheel 6 i ⁇ held in the gear 1 exclu ⁇ ively by the three ⁇ econd gearwheel ⁇ 10. These gearwheels 10 centre the fir ⁇ t gearwheel 6. The fir ⁇ t gearwheel 6 is therefore mounted without a journal. Although a certain friction does also occur between the first gearwheel 6 and the second gearwheels 10, this friction is also relatively uncritical, because it occurs only briefly at individual teeth. The tooth in question then becomes free again and is able to cool down in the surrounding fluid until the next engagement.
• the first gearwheel 6 i ⁇ provided only in the region of its end face remote from the motor 2 with a thin layer 17 of a friction-reducing plastics material, in particular PEEK. Relatively small axial forces are therefore absorbed. Friction between the ⁇ econd gearwheel 6 and the carrier 11 can be kept small.
• the leakage fluid flows in that case along the driven shaft
• the carrier 11 is connected non-rotatably to a driven shaft 20 of the gear 1. If the driven ⁇ haft 9 of the motor 2 i ⁇ now turned, the fir ⁇ t gearwheel 6 is also caused to rotate. It meshe ⁇ with the ⁇ econd gearwheel ⁇

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• Engineering & Computer Science (AREA)
• General Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Thermal Sciences (AREA)
• Gears, Cams (AREA)
• Rotary Pumps (AREA)

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• 1995
  • 1995-09-05 DE DE1995132722 patent/DE19532722C2/de not_active Expired - Fee Related
• 1996
  • 1996-09-04 WO PCT/DK1996/000365 patent/WO1997009514A1/en active Application Filing

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