GB2227078A - Hydrodynamic coupling - Google Patents

Description

j 1 dw I- Hydrodynamic coupling :::_ 1,21:2 7 tz) 7-

The invention is concerned with a hydrodynamic power transmission unit, In particular a hydrodyinamic.coupling in accordance with the preamble to Claim 1. A coupling of this species Is known from the DE-PS 26 14 476.

Vith the known coupling the problem Is to be solved, In order to prevent overloading the driving equipment upon a sudden alteration in the r.p.n. of the primary Inpellar, in particular upon a rise In the r.p.=., of very rapidly at least partially emptying the working space which nay be filled from outside in an open circuit. For doing that the coupling exhibits at least one euptying-channel which leaves from the outer region of the profile of the working space, leads radially Inwards Inside the coupling shell towards the axis of the coupling and opens out to atmosphere In the region of the hub. At increased r.p.n. and higher torque or slip, part of the operating liquid can thereby escape. This Imparts to the known coupling a safety function In the sense of a limitation of the torque which can be transmitted.

Further, from the DE-PS 969 722 a coupling is known, which is equipped with an emptying-valve which my be controlled by an external switching signal. This control valve Is arranged at the outer circumference of the coupling and Is connected by one side of the valve body to the working space. The valve body Is controlled through a channel which is connected to the supply device for the working space, that is, the feed channel for the operating liquid. This connecting channel furthermore exhibits a drilled permanently open outlet hole through which a certain amount of the operating liquid permanently flows away. But this discharge through a permanent outlet Is effected without the operating liquid having flowed through the working space. Hence the aforesaid control valve represents the sole device for emptying the working space, by the lowering of the pressure in the feed lead bringing about the opening of the control valve and hence the emptying of the 'coupling. But what Is disadvantageous In the case of this arrangement Is that renewed filling of the working space claims a relatively long tine because at the sane tine as the working space the feed lead to the control valve must also be filled and further, liquid flows away once more through this sane lead. For fast gearchanges e.g., in a notor vehicle drive, this coupling Is unsuitable.

The problem underlying the Invention is to create a coupling which is k suitable for the drive of a motor vehicle, especially of a tractor with an auxiliary power take-off. In detail what Is to be achieved is that through external control of the feed of operating liquid, separation of the flow of power for the travelling drive occurs as rapidly as possible without preceding reduction in the engine r.p.a., so that the flow of power to the auxiliary power take-off is maintained. It shall further be possible for the travelling drive to be able to be reengaged at any time, in particular at high engine r.p.n.

This problen is solved by the characterizing features from Claim 1. In accordance with the Invention at least one control valve which on its own Is known, Is arranged on the primary inpellar. The valve body of this control valve Is held in the closed position by the force from a spring and the pressure in a control lead which leaves from the catcher-groove. For opening the valve body the prerequisite Is: Ion-existence of pressure In the control lead. Opening Is then brought about:

a) at high engine r.p.n. through mechanical centrifugal force; and b) at relatively low engine r.p.n. solely through the pressure from centrifugal force upon the liquid.

The catcler-g.roove arranged running round on the prinary Inpellar, via which operating liquid Is fed under external control, is subdivided in accordance with the Invention, looking along the circumference, Into separate regions or chanbers, where the Inlet channel to the working space leaves'fron one region and the control lead to the control valve leaves from the other region of the catcher groove.

Vith this arrangenent the following Is achieved:

Assuming the primary side Is rotating, filling of the coupling which at first Is enpty is effected by feeding operating liquid Into the catchergroove. Both regions of the catcher-groove are thereby filled at the same time and operating liquid flows via the inlet channels into the working space and via the control lead to the control valve. At low engine r.p.a. the latter Is closed by spring force and at high r. p. m. is on the contrary opened by centrifugal force. In the latter case the subdivision of the catcher-groove into separate regions brings about a rapid build-up of k pressure in the control lead and hence rapid closing of the control valve Hence rapid filling of the coupling Is possible. The supply of operating liquid is maintained during operation and excess liquid led away through the permanently open outlet bore fron the working space. Further, a certain flow of liquid escapes permanently via a nozzle which is arranged at the end of the control lead leading to the control valve.

For emptying the coupling the feed of operating liquid to the catchergroove is interrupted. The one region of the catcher-groove thereby empties Itself Into the working space (in the sense of a filling process) whilst Independently of this the other region from which leaves the control lead to the control valve, empties by centrifugal force via the aforesaid nozzle. The emptying of this region is effected relatively rapidly since as already mentioned the two regions of the catcher-groove are separate from one another. The pressure in front of the valve body Is thereby lowered and the control valve opens and takes care of rapid emptying of the working space. In doing so the pressure In the working space from centrifugal force overcomes the closing force of the spring at average engine r.p.n. At higher engine r.p.n. through mechanical centrifugal force the valve body has already lifted fro= Its seat against the force from the spring after the pressure In the control lead has dropped. At low engine r. p. m. the spring force in the control valve Is greater than the pressure in the working space from centrifugal force, whereby the coupling remains filled.

The advantage of this arrangement consists In the control lead to the control valve becoming rapidly emptied after imterruption of the feed of operating liqu ld, because the subdivision of the catcher-groove Into individual regions does not allow any afterflow of the liquid from the other region. The regions connected by the Inlet channels to the working space only empty into the working space and not at the same tine Into the control leads. The control valve can thereby react conparati'vely rapidly to an emptying control conmand and bring about a relatively early opening of the control valve.

Upon building the coupling in accordance with the invention Into the drive of a notor vehicle, e.g., a tractor, the advantage thereby results of rapid separation of the travelling drive with the power take-off shaft 1

Claims (11)

still running. In this case the driver does not need either to actuate a possibly available mechanical coupling or to disengage the gear engaged at the tise. Further, stopping and gentle restarting of the vehicle at any engine r.p.ia. is possible without interruption of the auxiliary power take-off and without actuation of the rpechanical coupling and without changing gear. This yields a significant reduction in the frequency of changing gear and thereby a reduction In wear in the driving equipment. All of the properties hitherto known of a travelling drive with a hydrodynamic coupling. that is. reduction in vibration. prevention of stalling the engine and the possibility of tow-starting the engine are maintained. In accordance with Claims 2 and 3 the catcher-groove may either be subdivided Into separate regions through partitions arranged radially or be subdivided Into axially separate annular chambers by a partition arranged - with respect to the axis of rotation of the coupling - in a plane normal to it. Progressive refinements of the Invention are portrayed In the Sub-Claims. In accordance with Claim 4 it nay be of advantage if the two separate regions of the catcher-groove into which the inlet channel to the working s.Dace and the control lead to the control valve respectively open, are equipped with different volumes, in which case In accordance with Claim 6 the control lead to the control valve leaves from the smaller region and the inlet channel to the working space from the larger region. In accordance with Claim 7 It Is of advantage 11 the Inlet channel from the one region of the catcher-groove to the working space Is directed essentially radially and opens out into the working space near the inner wall of the profile of the blading of the primary inpellar. Claims 8 and 9 describe advantageous possibilities for the construction of the permanent outlet opening fro= the working space to atmosphere. In accordance with Claim 8 It Is foreseen that the valve body of the control valve should be made with a taper seat because this exhibits better sealing properties and tends less to fouling. The Invention Is explained in greater detail below with the aid of the drawing which shows one embodiment. There Is shown in: Figure 1 - a longitudinal section through the coupling in accordance with the Invention; 1 Figure 2 - a front elevation with representation of the sectors of the catcher-groove; Figure 3 - a longitudinal section through a catcher- groove of alternative construction; and Figure 4 - a section through the control valve. The coupling 1 represented In Figure 1 exhibits a primary impellar 2 connected to a driving machine which Is not shown. and a secondary impellar 4 with a hub. The two inpellars 2 and 4 fora a toroidal working space 6 provided with blades 5. A housing shell 3 Is connected to the primary impellar 2 to revolve with It and encloses the secondary wheel 4. Outside the primary inpellar 2 and radially inside the working space 6 lies a catcher-groove 7 open radially Inwards, Into which from a filler lead 15 represented diagrammatically a variable flow of oil nay be fed. Fron the catcher-groove 7 inlet channels 10 lead Into the Interior of the working space 6. Preferably these Inlet channels 10 run in the radial direction so that they open out at about the inner wall of the profile of the working space 6. At the outer circumference of the primary Inpellar 2 control valves 8 are arranged and connected via ccmtrol leads 9 to the catcher-groove 7. In the present embodiment eight control valves 8 and a like nunber of Inlet channels 10 are provided. From the working space 6 permanent outlet openinEs 11 in the primary inpellar 2 lead to atmosphere in which case they leave from the radially inner cmntour of the profile and open out radially outside the catcher-groove 7. As nay be seen In particular from the end elevat4= in Figure 2, the catcher-groove 7 Is subdivided by radial partitic=s 12 Into Individual regions 13. 14. The position of the partitions 12 and the number of then Is so chosen that regions of different sizes arl-se. that Is, as many larger and smaller regions as there are Inlet etatnels to the working space or respectively control leads to the contrcl valves. The Inlet channels 10 to the working space 6 leave from the larger regions 13 and the control leads 9 to the control valves 8 fron the smaller sectors 14. In the region of the permanent outlet mouths 11 tie partition walls 12 are thickened as shown. In Figure 4 a control valve 8 is represented in greater detail. It Is screwed radially Into the primary inpeller 2 fror outside and is connected to te working space 6. The control lead 9 opens into the upper part of a valve housing 16 In channels 17. Pron there a nozzlelike outlet 18 leads to atmosphere. Inside there is a mvable valve body 19 the tapered valve seat 20 of which Is acted upon In the opening direction by the pressure from the operating liquid in the working space 6. In the closing direction a spring 21 acts upon the valve body 19, assisted by the pressure from the control lead 9. Behind the valve seat 20 is a chamber 22 which Is unloaded to atnosphere via outlet openings 23. For filling the coupling operating liquid is fed via the catcher-groDve 7 through the filler lead 15. In the event of the engine r.p.m. being low at the time the control valve 8 is closed through the force from the spring 21 In the valve body 19. The small regions 14 of the catchergroove 7 fill very rapidly and the pressure In the control lead builds up whilst the level of liquid In the larger region 13 from which the inlet cliannels 10 lead to the working space 6 Is very low or has not yet adjusted itself. IS the coupling is filled at high engine r.P.2a. the pressure appearing In the small region 14 and hence in the control leads 9 closes the control valve 8 against the cent,-lfugal force from the valve body 19. The filling process is thereby speeded up. For emptying the coupling the feed of operating liquid Is Interrupted. The control lead thereby empties rapidly via the tozzle bore 18 and only the volume from the small region 14 has to escape. whereby the control valve 8 can open rapidly. During this tine the larger region 13 first of all empties Into the working space. ConnunicatIcm between the regions 13 14 Is advantageously prevented by the partitions 12 and the ability of the coupling to react to external control con--ands Is speeded up. Figure 3 shows another kind of subdivision of the catcher-groove 7 Into two annular chambers 7a and 7b. For doing that an annular partition 12a Is provided, arranged in a plane directed normally to the axis 25 of rotation of the coupling and hence subdivides the catcher-groove 7 into two axially separate annular chambers. In that case the Inlet channels 10 Into the interior of the working space 6 leave iron the larger annular chambers 7a and the control leads 9 to the control valve 8 leave from the i z k_ i 1 smaller annular chamber 7b. The method of operation corresponds with that of the catcher-groove 7 with partitions 12 and regions 13 and 14. In case of need It Is possible to start the engine by towing the vehicle by means of a second vehicle. In this case the primary inpellar 2 Is at first stationary and the secondary inpellar 4 Is driven from the driving wheels. Thus the functions of the primary and secondary inpellars are now interchanged. Since there Is a sufficiently large residual amount of operating liquid In the working space 6 and the control valves 8 are closed by means of spring force the torque which can be transmitted by the coupling is adequate for starting the engine. 1 t 8 Claims: 1. A hydrodynamic power transmission mechanism. in particular a hydrodynamic coupling, having the following features: a) a primary impeller and a secondary impeller which together embrace a toroidal working space; b) on the primary impeller there is an annular catcher-groove into which a filler-lead opens for the controlled feed of operating liquid and from which at least one inlet channel extends to the working space; c) the coupling includes at least one permanently open outlet opening in one of the impellers as well as a further emptying device; d) the further emptying device is constructed as at least one pilot valve on the primary impeller which is connected via a control lead to the catcher-groove and which may be brought into the closed position by the force from a spring as well as into the open position by the pressure from centrifugal force upon the operating liquid in the working space; e) the catcher-groove is sub-divided by at least one partition into regions separated from one another, the inlet channel to the working space extends from one region and the control lead to the pilot valve extends from the other region.

1 9

2. A coupling as claimed in claim li wherein. by means of radially directed partitions. the catchergroove looking in the circumferential direction. is sub-divided into said separate regions.

3. A coupling as claimed in claim 1. wherein. by at least one partition arranged in a plane perpendicular to the axis of rotation of the coupling, the catcher-groove is sub-divided into two annular chambers arranged side-by-side axially.

4. A coupling as claimed in claim 1, 2 or 3, wherein the regions exhibit different volumes.

5. A coupling as claimed in claim 4r wherein the volume of the larger region is at least twice the volume of the smaller region.

6. A coupling as claimed in claim 4 or 5, wherein the inlet channel to the working space extends from the larger region and the control lead to the pilot valve extends from the smaller region of the catcher-groove.

A 1 1

7. A coupling as claimed in any preceding claimr wherein the inlet channel from the catcher-groove to the working space is directed essentially radially and opens into the working space near the inner profiled wall of blading on the primary impeller.

8. A coupling as claimed in any preceding claim, wherein the permanent outlet opening extends from the radially inner region of the profile of blading of one of the impellers in an oblique direction towards the axis of rotation of the coupling and opens to atmosphere radially outside the catcher-groove.

9. A coupling as claimed in claim 8. wherein the permanent outlet opening is on the primary impeller.

10. A coupling as claimed in any preceding claim, wherein the pilot valve has a valve body with a valve seat formed on a taper.

11. A hydrodynamic coupling substantially as hereinbefore described with reference to the accompanying drawings.

Published iggoatThepatentotace,StateI-Iouse.66,71 HIghHolbom. London WC1R 4TP. Further copies maybe obtainedfrom The Patent Mice Sales Branch, St Mary Cray. Orpington, Kent BR5 3RD- Printed by Multiplex techniques ltd. St Mary Cray. Kent, Con 187 Sales Branch. St Marv Cra-v. Urpingron, AenL nrbo Oktii- rTinTCCL py inumplex wrxuuqucb J. 0h -y iav. VA&b, V- --- 1