GB2259338A

GB2259338A - A drive device for an auxiliary of a prime mover comprising epicyclic gearing of which one element drives a throttled pump

Info

Publication number: GB2259338A
Application number: GB9217118A
Authority: GB
Inventors: Volker Doring
Original assignee: Daimler Benz AG; Mercedes Benz AG
Current assignee: Daimler Benz AG
Priority date: 1991-08-28
Filing date: 1992-08-13
Publication date: 1993-03-10
Anticipated expiration: 2012-08-13
Also published as: DE4128543C2; ITRM920618A1; DE4128543A1; FR2680829B1; GB9217118D0; GB2259338B; ITRM920618A0; IT1258463B; FR2680829A1

Abstract

A drive device for at least one auxiliary of a prime mover consists of an epicyclic gearing 3, 4, 5, 8 in which one component is rotatably supported on the casing 7 by means of a torque which can be changed. in order to permit. the transmission ratio of the drive device to be changed within a maximum band width using simple means, it is proposed that the device for changing the support torque be designed as a fluid displacement pump 10 whose delivery can be controlled. The teeth of a ring gear 4 preferably mesh with an inner gear 9 forming part of the pump as well as with epicyclic gears 6. <IMAGE>

Description

1 - ' C ' ' c 1 A drive device for an auxiliary of a -Prime rover The

invention concerns a drive device for at least one auxiliary of a prime mover with an epicyclic gear which has an input unit, an output unit and a further unit supported on a casing and with a device for changing, as a function of operating parameters, 'he torque by means of J_ L- --ed on the casing.

which the further unit is support A drive device of this type for the fan of an internal combustion engine is kncwn -Erom Ger-man patent application P 40411-1-58.3-13. This provides for the inner -ral wheel of tha epicyclic gear to be supperted on the ceni L-A 1 internal co-mbustion engine casing via a hydrodyna-mic brake, it being possible &to vary the support torque, and therefore the fan speed, relative to a certain internal co-mbustion engine speed, by a corresponding change to the filling ratio the hydrodynamic brake. Because the rotor of a of t 1 ' hydrodynanic brake can never be brought completely to rest even with maximum filling, it is also inpossible to utilise e Input/output he theoretically possible widt"", of t- k_ transmission r a -,L-. i o. From German 0.-LP-LP=-nlegungsschri.1L-L.

L- ---hetransmission ratio 38 21 367, it is also known &to vary 4-11 of a step-up gear by means of a hydraulic motor coupled to the inner central wheel of epicyclic gear, t h ii s hydraulic motor being driven by a pump driven by tl-.e internal combustion engine itself. This, however, reuresen-tt--s a relatively cost-intensive solution.

The present invention seeks to creat-e a drive device, of the type described in the first paragraph, in which the transmission ratio can be varied within a -,,ax-irum band width by simple means.

According to the present invention there is provided L - leas' one auxiliary of a prine mover, a drive device for at t_ - with an epicyclic gear which has an input unit, an output unit and a furt.her unit suppc;:ed on a casing and with a device for changing, as a function of operating parameters, 2 the torque by means of which the further unit is supported on the casing, wherein the device for changing the support torque is a fluid displacement pump whose delivery is controllable and which is driven by the further unit.

The use of a liquid displacement pump whose delivery can be controlled has the advantage that by reducing the delivery of the pump to zero., it is possible to bring to rest the.unit of the epicyclic gear which is supported on a stationary casing with the pump as intermediary. With this solution, therefore, the transmission ratio of the drive device can be varield within -Lthe maximum possible band width. The use of a simple pump also provides a relatively inexpensive solution and in the case where the pump is integrated as an inner gearwheel pump in the casing of the epicyclic gear, it is also possible to economise in ins'Lalia.tL-icn space. By using a suitable valve device located in a delivery conduit connected to the pressure side of the pump, 'he delivery - or the pressure in this conduit - and tL.L J_ -he speed of the pump can be changed relatively here-Ecre tll rapidly. It is therefore possible to achieve a very rapid change in the transmission ratio if required.

Using a pressure limiting valve upstream of a valve device controllIng the delivery as a function of operating paranneters of the prime mover has the effect that -'L---he auxiliary can be driven at high pcwer even at low input speeds but damage to the auxiliary at high input speeds can always be excluded. It is therefore possible to limit power of the particular auxiliary, for example a fan, in a simple manner.

In a preferred embodiment, the suction spaces of the -o a lubrcating oil reservoir space pump are connected 4L L provided in the casing of the epicyclic gear by means of openings located in the sealing plate, which space is connected to the lubricating oil circuit of the prime mover.

This embodiment has the advantage that it is nct necessary to provide a separate f- d circuit to operate the pump according to the In addition, the heat arising 3 due to the energy loss can be removed in a simple manner by means of this embodiment.

An embodiment of the invention will now be described by way of example with reference to the drawing in which:- Figure 1 shows, in a diagrammatic cross-section, a device according to the invention for driving a fan of an internal combustion engine, Figure 2 shows a sectional representation from Figure 1 along the line IIII and Figure 3 shows, in a PI-1 f(n) diagram, the relationship between the fan power P, and the internal cc,-,,bus-l'--ion engine speed n.

Figure 1 shows a step-up gear 1 for a fan 2 of an internal combustion engine, which is not visible in -41-2he drawing. This s-IEep-up gear 1 is an epicyclic gear which consists of an inner central wheel 3, a planet wheel carrier 5, on which planet wheels 6 are rotatably supported, and an outer central wheel 4. The inner central wheel 3 is torsionally connected to the fan 2 and the input takes place via the planet wheell carrier 5, which is t-orsionally connected to 'L--he crankshaft (again not visible in the drawing) of the internal co-.,,b,,is-l'--ion engine. Thle casing 7 accommodating the individual components of the step-up gear L is supported against the casing 8 of the internal combustion engine (only represented symbolically in this -p ' 1 A figure). The outer central whee. is made rela-ICively wide so 'hat in addition to the planet wheels 6, t-he inner gearwheel 9 of a fluid displacement inner gearwheel pump 10, which is likewise arranged in the casing 7, can engage in its internal teeth. The outer central wheel At, therefore, also forms the outer gearwheel of the inner gearwheel pump 10. The sealing of the inner gearwheel 9 takes place, on the one hand, by the epicyclic gear casing 7 itself and, on the other, by a sealing plate 11 permanently connected to the casing 7 and located between the inner gearwheel 9 and the plane of motion of the plane';'_wheels 6. This sealing plate 11 protrudes into an internal groove 12 provided in the 4 outer central wheel 4. The inner gearwheel 9 is supported in the sealing plate 11 at one end and directly in the easing 7 at the other. It m ay be seen f rom Figure 2 that the epicyclic gear casing 7 surrounds the inner gearwheel 9 in such a way that two spaces 13 and 14 are separated fromm one another by the inner gearwheel 9. An assumed rotation of the outer central wheel 4 in the direction of the arrow 15 causes a rotation of the inner wheel 9 in the direction of the arrow 16 so that -'Che fluid to be delivered (in this case, engine oil) is taken up by the teeth of the inner gearwheel 9 from 'he space 13 - and correspondingly from the space 13' by 'L--he teeth of the outer central wheel 4 - and transported into the space 14. Because -L'--he teeth of the inner gearwheel 9 come into engagement again with the teeth of the outer central wheel It after passing 4C11 e s p a c e 14, the engine oil located in the Ceeth of the gearwheels 4 and 9 is pressed out so that a positive pressure appears in the space 14. The space 14 therefore forms the pressure space and the spaces 13 and 131 ','-.-he suction spaces of the inner gearwheel pump 10.

Each of the suction spaces 13 and 131 is connected to the space 18 (Figure 1) of the epicyclic gear by means of a respective passage hole 17 or 171 (Figure 2) located in the sealing plate 11. This space 18 is, in turn, connected to the lubricating oil circuit of the internal combustion engine. This ensures that the filling level in the epicyclic gear casing 7 can never fall below the level shown by the interrupted line 19. Any induction of air by the pump 10 via the passage holes 17 and 17/ is therefore excluded. At the sane tire, there is always optimum lubrication of the individual components of the epicyclic gear.

In a further embodiment of the invention, it is also possible to extend the sealing plate over the whole of the internal diameter of -'the outer central wheel so that the space in which the planetary gearwheels run is separated in a liquid-tight manner fre,,-, the space in which the inner gearwheel pump runs. In this case, a fluid can be used for operating the inner gearwheel pump which is different from that required for lubricating the epicyclic gear. The outer central wheel must then, of course, be designed so that it can be split (for assembly reasons).

A hole 20 is located at the level of the pressure space 14 in the epicyclic gear casing 7 and a delivery conduit 21 is connected to it. The flow cross-section of the delivery conduit 21 can be steplessly controlled by means of a valve device 22 and, in fact, between a position which reduces the cross-section to zero (closed position) and a position which fErees the complete cross-section of the conduit 21 (maximum opening position). The valve device 22 is activated by neans of an electronic control unLt- 23 as a function of operating parameters of the internal combustion angLne which are supplied to -'L--he control unit 23 via the measurement conductors 24. Such parameters are, for example, the internal cc-,i.bus.IL-icn engine load, the inlCernal combustion engine speed, the coolant temperature of the internal combustion engine, the temperature of an additional braking device connected to the internal combustion engine, such as a retarder, the boost air temperature, the oil temperature, etc. Downstream of 'L--.he valve device 22, the delivery conduit 21 opens into t-he lubricating oil reservoir of' the internal combustion engine (arrow 25) or is fed back into the casing 7 in the case of a separat- e oil return to the lubricating Oil reservoir of the internal combustion engine. The output speed of the epicyclic gear, and therefore the fan speed, now depends - relative to a certain input speed - on the torque with which the outer central wheel 4 is braked or supported. This torque in turn depends directly on the back L- - 21 and therefore on the pressure in the delivery conduit 11 opening position of the valve device 22. If the latter is in i t_s maximum opening position, the pump 10 can deliver at its raximum. rate. The back pressure in the delivery conduit 21 is therefore a minimum, i.e. the speed of the inner gearwheel 9 is a maximum and, in consequence, the braking torque on the outer central wheel 4 is a minimum.

6 If, on the other hand, the valve device 22 is in its closed position, the pump 10 can no longer deliver any engine oil, i.e. the inner gearwheel 9 can no longer rotate. The outer central wheel 4 is, in consequence, also at rest because it is now indirectly supported (via the bearings of the inner gearwheel 9) on the casing 7 via the incompressible engine oil located on the pressure side.

There is a proportional relationship between the pressure in the delivery conduit 21 arik,AI the speed of the outer central wheel 4. In consequence, the torque with which the outer central wheel 4 is supported - and therefore the output speed (speed of the inner central wheel 3) - can be steplessly varied by changing the opening position of the valve device 22.

If the internal combustion engine is now operated at a certain speed n, the planet wheel carrier 51 naturally rotates at the same speed. The peripheral speed at the outer periphery of the planet wheel carrier 5 (radius r,.) then corresponds to the length of the arrows 26 and 27 in the two diagrans A and B of Figure 1. The peripheral speeds v of the the epicyclic gear are plotted -4ng parts of tll individual rotaik L J_ k_ XA in these diagrams A and B as a function of the radius r of the particular wheel (r--- radius of the outer central :=t wheel 4, r,,, = radius of the planet wheel carrier 5 and r-L L radius of the inner central wheel 3).

The relationships when the valve device 22 is at maximum, opening are shown in diagram A. In this case, a maximum flow of oil can be delivered, i.e. the speed of the inner gearwheel 9 is a maximum and, in consequence, the torque with which the outer central wheel 4 is braked is a minimum. The outer central wheel 4 therefore rotates at a relatively high speed. The peripheral speed in this case is shown by the arrow 28 in diagram A. If the points of the two arrows 28 and 26 are connected together, the arrow 29 ai- the radius ri of the inner central wheel 3 gives a peripheral speed v which is relatively small. (The length of the arrow is a measure of the magnitude of the peripheral speed v at 7 the particular radius r--,, r or r-L.) The output speed of the epicyclic gear, and hence the fan speed, is therefore also relatively small in this case.

If the delivery conduit 21 is now closed by the valve device 22, the inner gearwheel 9 of the gearwheel pump 10, and therefore also the outer central wheel It, will be brought to rest, i.e. the peripheral speed v at the radius - the radius 3 0 at r_. becomes zero. Connecting the zero point r,:,, to the point of the arrow 27 in the diagram B therefore gives a peripheral speed v at the radius r j of '%he inner central wheel 3 which is now higher and, in consequence, gives an increased fan speed (arrow 36).

Relative to a certain input speed or peripheral speed at the radius rM of the planet wheel carrier 5, the output speed or peripheral speed at the radius r j of the inner central wheel 3 is a maximum when the peripheral speed v at the radius r,,, of the outer central wheel 4 is zero, L- rest. As the speed i.e. when the outer central wheel 4 is at of the outer central wheel It becomes 'Larger, the output speed of the epicyclic gear, and therefore the fan speed, becomes smaller.

It is, of course, impossible to avoid very small leakage losses at the pressure side of the gear pump 10 completely, i.e. the inner gearwheel 9 can still move slightly even when the valve Idlevice 22 is closed, but the resulting effect on the output speed of the epicyclic gear is insignificant.

In a further embodiment of the invention, it is similarly possible to provIde a pressure limiting valve 31 (shown by an interrupted line) upstream of the valve device 22. This prevents a limiting value for the back pressure in the delivery conduit 21 being exceeded upstream of the valve device 22 and therefore prevents a -'fan speed which is excessive as regards the strength. The pressure limiting L ---hatwhen the specified valve 31 functions in such a way 4-11 limiting value for the back pressure is reached, some engine oil is released via the lim-Lt4Lng valve 31 and, in fact, pre- 8 cisely that quantity which is necessary to prevent the limiting pressure in the conduit 21 from being exceeded. This., therefore, effects a power limitation.

Figure 3 shows, in a diagram 32 of P-r.=f(n), the relationship between the fan power P T. and the internal combustion engine speed n in the case where the valve device 22 is at maxintun, opening (full line graph 33) and in the case where the delivery conduit 21 is closed by the valve device 22 (interrupted line graph 34). When the conduit 21 is closed, the fan speed, and therefore the fan power PTt is always greater than it is when the delivery conduit 21 is open. The graph 34 therefore lies above the graph 33 for every internal combustion engine speed n. The pressure limitation valve 31 can be used, when the conduit 21 is closed, to rake the fan power curve run almost' hor4Lzon-&'--ally fro-in a specified threshold value n., of the engine speed.

MI- M,is is indicated by the chain-do41---'L.-ed line 35 in the diagram of Figure 3. This solution makes it possible to operate the fan 2 fully switched on - if necessary - over the w.hole of L Lthe speed range (i.e. when the delivery conduit 21 is closed by the valve device 22) so that virtually the maximum fan power PM,,-rx,,,:,, is achieved even at a relatively low internal combustion engine speed n CS. The possibility -'t..--hat the fan might be damaged by excessive speeds in the higher internal combustion engine speed range is, however, always excluded. By means of this solution (controllable valve device 22 and upstream pressure limiting valve 31), however, any given point between the three graphs 33, 34 and 35 can be reached if required. The pressure limiting valve 31 does not necessarily have to be located in series with the controllable valve device 22; it can also be connected in parallel with it. The use of a pressure limiting valve 31 also has the advantage that the overall system can react particularly rapidly when the limiting value for the back pressure in the delivery conduit 21 is exceeded.

The kink in the curve can also be achieved without using a pressure li-iting valve 31 but a separate sensor 9 must then be provided in the delivery conduit 21 upstream of the valve device 22. This sensor is used to transmit the current back pressure to the electronic control unit 23 which, when the limiting pressure is reached at the internal combustion engine speed threshold value n controls the valve device 22 in such a way that the chain-dotted curve 35 is achieved in the delivery conduit 21 by correspondingly freeing the flow cross-section. The control can also take place by means of a sensor recording the fan speed.

In a further embodiment of the invention, it is also conceivable to provide only a pressure limiting valve, which releases the corresponding oil flow when reaching the limiting pressure, in the fluid delivery conduit 21. By this means, the interrupted line graph 34 would be followed from the idling speed nT T. up to the limiting speed n,,,,; and the chaindot-'L-ed graph 35 would be followed at higher speeds.

Instead of a gear pu-,,p, a vane pump, in which the vanes nay or may not rotate, can be used as the fluid displacement pump. TA1here the vanes do not rotate, the displacement elements can be located on the back of the outer central wheel and the vanes can be "Located in -'L--he casing. Where the vanes rotate, the casing rust be an excen4trically machinedl casing and a vane must be located in the outer central wheel.

It is, of course, not imperative for the variable support of the torque to take place at the outer central wheel of the epicyclLc gear. It can also take place at another component in a manner according to the invention. The input and output must then be displaced correspondingly.

claims 1. A drive device for at least one auxiliary of a prime mover, with an epicyclic gear which has an input unit, an output unit and a further unit supported on a casing and with a device for changing, as a function of operating parameters, the torque by means of which the further unit is supported on the casing, wherein the device for changing the support torque is a fluid displacement pump whose delivery is controllable and which is driven by the further unit.

Claims

2. A drive device according to Claim 1, wherein the input unit is the

plane-';_- wheel carrier, the output unit is the inner central wheel and the further unit is the outer central wheel of the epicyclic gear.

3 A drive device according to Claim 2, wherein the fluid displacement pump is an inner gearwheel pump whose outer gearwheel is formed by the internal teeth of the outer central wheel of the epicyclic gear.

4. A drive device according to Clain, 3, wherein the width of -'L---he internal teeth of the outer central wheel is greater than the width of the teeth of the planet wheels and adjacent to the plane of motion of the planet wheels, tChe inner gearwheel of the pump is in engagement with the internal teeth of the outer central wheel, the sealing of the inner gearwheel of the pump taking place by means of the casing itself and by means of a sealing plate which is located between the plane of notion of the planet wheels and the inner gearwheel of the pump, which is permanently connected to the casing and which extends into a peripheral internal groove located in the outer central wheel.

5. A drive device according to any one of Claims 1 to 4, wherein the pressure space of the pump is connected to a 11 fluid delivery conduit whose flow cross-section is controllable by means of a valve device.

6. A drive device according to Claim 5, wherein a valve limiting the pressure in the delivery conduit upstream of the valve device is located upstream of the valve device.

7. A drive device according to Claim 1, wherein the suction spaces of the pump are connected to a lubricating oil reservoir space provided in the casing of the epicyclic gear by means of openings located in the sealing plat-e, which space is connected to the lubricating oil circuit of the prime mover.

8. A drive device for at least one auxiliary of a prime mover, substantially as described herein with reference to and as illustrated in the accompanying drawings.