GB2159914A - Hydraulic retarder - Google Patents

Abstract

The retarder is based on a principle of a centrifugal side channel high pressure pump designed for zero delivery, and it comprises relatively rotating parts (20, 28) defining an annular chamber (24) between them filled with hydraulic fluid, one of the parts (20) having radial vanes (30, 31) thereon and the other part (28) having at least one gate (32) displaceable into the fluid chamber, the or each gate (32) being such that it can be withdrawn completely from the fluid chamber (24) to leave the latter substantially unobstructed, and means (38, 40, 42, 44, 46, 48, 50) are provided operable externally of the retarder for varying the extent to which the gate is displaced into the chamber. When the or each gate (32) is fully withdrawn from the fluid chamber (24), there is no bodily movement of the hydraulic fluid relative to the vaned part (20) thereby reducing energy dissipation to a minimum. The gates (32) can be partially retracted to obtain a reduced retarding torque. <IMAGE>

Description

SPECIFICATION Hydraulic Couplings The present invention relates to hydraulic retarders and couplings.

Hydrodynamic brakes or retarders which work on a similar principle to hydrodynamic couplings are well known. The braking force is achieved by retarding the inertial force of the working fluid which is accelerated radially and tangentially in the driven rotor and decelerated in the stator The braking force can be varied by varying the amount of fluid in the retarder.

Any friction orfluid coupling can be used as a brake. The effectiveness of a fluid brake depends upon the speed of rotation. A fluid brake becomes inefficient at low speed and ineffective at zero speed. For this reason it is usually called a retarder.

A retarder is often used at high speeds for heavy loads because there is no lining wear and because it is easy to cool. It may be used in conjunction with a friction brake which is operated only at low speeds.

Brake lining wear is thereby much reduced.

The known hydrodynamic retarders are provided with "scoop-control", hydraulic pumps or a compressed air system for filling and emptying, which is large and cumbersome and timeconsuming. The size is disadvantageous not only from the cost point of view but also makes installation and design difficult, particularly in the case of a vehicle where the retarder is to be installed on the propeller shaft or thereabouts. The time taken for filling and emptying makes for slow response and space is required for storing the fluid emptied from the retarder.

Furthermore, the known hydrodynamic retarders offer a significant torque even when they are empty of the hydraulic fluid. This is because of the air which is pumped between the fixed and moving parts by the vanes or blades in these parts.

The present invention seeks to provide a hydraulic retarder which is cheaper and smaller than a conventional hydrodynamic retarder designed to give the same performance and which offers less resisting torque than known hydrodynamic retarders when it is not operated.

The present invention relates to a new hydraulic retarder based on the principal of a vortex or side channel pump which is designed for a closed circuit so that there is no filling and emptying.

The present invention resides in an hydraulic coupling suitable for use also as an hydraulic retarder; the coupling being of the kind employing the principle of a centrifugal side channel high pressure pump designed for zero delivery and comprising relatively rotating parts housed within a casing and defining an annular fluid chamber between them filled with hydraulic fluid, one of the parts having radial vanes thereon and the other part having at least one gate displaceable into the fluid chamber, characterised in that the or each gate can be withdrawn completely from the fluid chamber to leave the latter substantially unobstructed and in that the coupling provides means operable externally of said casing for varying the extent to which the gate is displaced into the chamber; whereby, when the or each gate is fully withdrawn from the fluid chamber to operate the coupling at zero delivery there is no bodily movement of the hydraulic fluid relative to the vaned part thereby reducing energy dissipation in the coupling to a minimum; and whereby, when the or each gate is displaced into the fluid chamber, the delivery of the coupling can be controlled by operation of said means. When the gate or gates are extended so that they protrude into the fluid chamber, a pressure difference is built up across the gate or gates to provide the resistance to rotation of the rotatable part. In embodiments where the part having the movable gate or gates is the rotatable part, the blades on the non-rotatable part act as turbine blades to take up the work done by the gate or gates rotating against the pressure difference.Conversely in embodiments wherein the part having the movable gate or gates is the non-rotatable part, the blades on the rotatable part act as impeller blades to pump the fluid and so create the pressure difference across the gate or gates.

The hydraulic retarder according to the present invention thus operates on the same principle to the hydraulic coupling or clutch described in British Patent No. 1528022 and 1561000, except for the provision of the arbitrarily adjustable and fully retractable gate or gates to enable the braking torque to be adjusted.

In the hydraulic brake or coupling according to the invention, the annular vortex chamber is kept full of hydraulic fluid at all times.

The gate or gates are adjustable substantially instantaneously so that response times are very rapid.

Hydraulic retarders according to the invention are ideal for buses and other town vehicles which start and stop frequently.

The gate or gates can be operated hydraulically, pneumatically, electrically or manually.

A simple adjusting means for the gate or gates, in embodiments wherein the part having the gate or gates thereon is or forms part of the rotor, comprises an input sleeve axially displaceable but non-relatively rotatably mounted on a shaft having the part or rotor thereon and an output element relatively rotatably but non-axially displaceably mounted on the shaft, a helical connection being provided between the sleeve and the element, whereby axial displacement of the sleeve causes the output element to be angularly displaced relative to the shaft, coupling means being provided between such element and the gate or gates. The sleeve can be axially arbitrarily adjusted while the rotor and shaft are rotating, to cause a corresponding adjustment of the gate or gates to adjust the retarding torque to a desired value.

The helic angle of the helical connection can be chosen so that the connection is self-locking or non-reversible. In other words, the sleeve can displace the gate or gates but the latter cannot displace the sleeve.

As an alternative to the sleeve and helical connection, a differential mechanism can be provided such that an angular displacement of an input sleeve relative to the fixed part causes a corresponding angular displacement of an output member relative to the rotatable shaft, irrespective of the speed of rotation of the latter.

The or each gate may be transversely slidably guided in said part and provided with a rack which meshes with a pinion on said output element.

However, the or each gate may be mounted to pivot into and out of the fluid chamber, and means are provided to bias the gate or each of them into the chamber under a predetermined loading, whereby in the event of an overload of hydraulic fluid acting on the gate or gates in a direction opposed to that in which the gate or each gate pivots into the chamber, the gate or each of them pivots against the biasing means to increase the fluid size of the fluid passageway past the gate or gates and thereby relieve the overload.

The invention is further described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a fragmentary longitudinal section of a hydraulic retarder according to the present invention; Figure 2 is a fragmentary cross section of the retarder of Figure 1, taken on line 1I--II of Figure 1; Figure 3 is a longitudinal sectional view, similar to Figure 1, but showing a second embodiment of the invention; Figure 4 is a longitudinal section, similar to Figure 1 but showing a third embodiment of the invention; Figure 5 is a cross section of the embodiment of Figure 4; Figure 6 is a longitudinal sectional view of a fourth embodiment of the invention, and Figure 7 is a fragmentary cross section of a further embodiment of the present invention.

Referring first to Figures 1 and 2 of the drawings, a hydraulic retarder in accordance with the present invention comprises a stator 20 which forms part of a casing 22. A shaft 26 is journalled by bearings in the casing 22 and carries a rotor 28 which includes a core 27. An annular side channel or vortex chamber 24 is defined between the stator 20 and the periphery 29 of the core 27. The stator 20 carries two annular rows of blades 30,31 around the annular vortex chamber 24 at opposite axial sides thereof.

The rotor core 27 carries three equi-angularly spaced gates 32, which are shown in their fully closed positions in Figure 2. Each of the gates 32 is slideably guided in a respective transverse groove 34 formed in the rotor core 27. Its outer end can co-operate with the outer peripheral wall 36 of the stator 20 and its inner end is provided with a rack 38 which meshes with a pinion 40. As can be seen from Figure 2, the racks 38 of all three gates 32 co-operate with respective portions of the toothed periphery of the pinion 40.

As shown in Figure 1, the pinion 40 is fixed to a tubular element 42 which is relatively rotatably but non-axially displaceably mounted on the shaft 26. A sleeve 44 encircles the element 42 and the shaft 26.

The sleeve 44 carries a pair of inwardly directed pins 46 which pass through helical slots 48 formed in the element 42 and penetrate axial grooves 50 formed in the shaft 26. The sleeve 44 is thereby rotated with the shaft 26 but may be axially displaced relative to the shaft 26 by means of a forked member (not shown) which engages a peripheral groove in the sleeve 44. Because the pins 46 engage through the helical slots 48, axial displacement of the sleeve 44 causes the tubular element 42 to be angularly displaced relative to the shaft 26. As can be appreciated from Figure 2, such angular displacement rotates the pinion 40 to retract or extend the gates 32. The helic angle of the slots 48 may be chosen so that the tubular element 42 cannot be angularly displaced by trying to push in or pull out the gates 24.

The vortex chamber 24 is kept filled with hydraulic fluid from a topping-up reservoir 80 which is connected by a duct 82 to an annular space 62 in the casing 22 and at one side of the rotor 28. Passages (not shown) in the rotor connect the space 62 to the vortex chamber 24.

The drawings are diagrammatic to illustrate the principles of the present invention but in practice the shaft 26 will be driven by the member to be braked. For example, the shaft 26 may be part of or coupled to the propeller shaft of a mechanically propelled vehicle. With the gates 32 fully retracted into the core 27 so that the outer tips of the gates are flush with the periphery 29 of the core 27, the rotor 28 can rotate freely. The skin friction between the core periphery 29 and the hydraulic fluid in the vortex chamber 24 is minimal since the core periphery 29 presents a relatively small surface area to the vortex chamber so that there is substantially no retarding force applied by the hydraulic retarder.

When the gates 32 are extended radially outwardly, as shown in Figure 2, the hydraulic fluid in the annular vortex chamber 24 is caused to rotate around this chamber. The vanes 30, 31 on the stator 20 then act in the same manner as in a hydraulic coupling as described in British Patent No. 1528022 to create a pressure difference across each gate 32.

The normal direction of rotation is clockwise in Figure 2 as shown by the arrow 52 and a higher pressure is formed in front of each gate 32 and a lower pressure behind each gate by virtue of the rows of blades 30, 31 acting as stationary turbine blades. The hydrostatic pressure difference applied to each gate 32 applies a retarding torque to the rotor 28. The retarding torque is maximum for a given speed when the gates 32 are fully extended as shown in Figure 2. To obtain a reduced retarding torque, the gates 32 can be partially retracted by axially displacing the sleeve 44 of Figure 1.

The hydraulic retarder according to the present invention is to be distinguished from the prior art hydrodynamic retarders in that the latter create a pumping action between the stator and the rotor and the power is dissipated by restriction of the fluid flow between the stator and the rotor. In the hydraulic retarder according to the present invention there are no vanes as such on one of the parts, namely the rotor in Figures 1 and 2, and it is the static pressure build up across the gates which creates the braking torque.

The embodiment of Fig. 3 is similar to that of Figs.

1 and 2 and like or similar parts are denoted by like reference numerals. The principal difference resides in the means for arbitrarily adjusting the gates which are arranged in the core 27 in the same way as is shown in Fig. 2. Hence, the pinion 40 with which the racks on the gates mesh, is identified in Fig. 3 by the same reference numeral. In Fig. 3, an input sleeve 45 is coupled by a differential gear mechanism 47 to an angularly displaceable output element 43 which has the pinion 40 thereon. This mechanism 47 comprises one or more input side planetary gears 49, one or more output side planetary gears 51 and a double ring gear 53 which meshes with all planetary gears 49, 51.The input side planetary gear or gears 49 are journalled to the input sleeve 45 so that their axes are angularly displaced about the shaft 26 by angular adjusting movements of the sleeve 45. The planetary gear or gears 49 mesh with a first sun gear 54 which is keyed to the shaft 26. The ring gear 53 is freely journalled on a bearing extension of the sun gear 54.

The output side planetary gear or gears 51 mesh with a second sun gear 56 which is formed on the output element 43. The planetary gear or gears 51 are journalled to the casing 22 so that their axes are fixed. The planetary gears 49,51 all have the same number of teeth, the sun gears 54, 56 have the same number of teeth and the two sets of teeth on the double ring gear 53 have the same number of teeth.

With the input sleeve 45 stationary, the sun wheel 54 drives the sun wheel 56 via the planetary gear(s) 49, the ring gear 53 and the planetary gear(s) 51.

This causes the sun gear 56 to rotate at exactly the same speed as and in the same direction as the shaft 26, so that the gates remain in their adjusted positions. If the input sleeve 45 is now angularly displaced, e.g. by means of a lever 54 fixed to the sleeve 45, through an angle a, the output element 43 is correspondingly angularly displaced through an angle ss relative to the shaft 26, irrespective of the speed of rotation of the shaft. It can be shown that ad (3=- a+c where a is the number of teeth on each of the sun wheels 54,56 and c is the number of teeth on each part of the double ring gear 53.

The double differential 47 provides a more positive adjustment than the helical connection shown in Fig. 1.

Usually, the hydraulic fluid will be oil or water, which may have suitable additives, e.g. to provide corrosion resistance or to prevent freezing. The topping up reservoir has been omitted from Fig. 3.

In the embodiments of Figs. 1 to 3, oil would be used as the hydraulic fluid since seals 19 seal the casing 22 to the shaft 26 outside the bearings, whereby the latter are immersed in and lubricated by such fluid.

Since the braking action achieved by the hydraulic retarder in accordance with the present invention must inevitably result in the hydraulic fluid being heated, provision must be made for cooling the fluid. In Fig. 1,a cooling jacket 21 is shown by dotted lines as disposed about the stator 20. This cooling jacket 21 can be connected in the cooling water system of the internal combustion engine in the case of a mechanically propelled vehicle. In Fig. 3, coolant chambers 23 are shown incorporated in the casing 20. The coolant may be the engine coolant.

The vortex chamber 24 of the hydraulic retarder shown in Figures 4 and 5 of the drawings is itself incorporated in the cooling system of the vehicle to which the retarder is fitted. More specifically, water is used as the hydraulic fluid and a small proportion of the fluid is circulated between the hydraulic retarder and the usual water cooling radiator. The hydraulic retarder of Figures 4 and 5 is constructed similarly to the embodiment of Figure 1, and like parts have the same reference numerals. The rotor core 27 rotates in the direction indicated by the arrow 52 in Figure 5. A higher pressure prevails in front of the gates 32a and a lower pressure behind the gates.The zones of the vortex chamber 24 in front of the gates 32a are connected by passages 60 in the rotor core 27 to an annular manifold chamber 62 formed between the rotor 28 and an inner peripheral portion 64 of the casing. A connector 66 on the casing communicates with the chamber 62 and can be connected by means of a hose (not shown) to the water inlet of the radiator. Similarly, passages 68 in the rotor core 27 connect the zones behind the gates 32a to an annular manifold chamber 70 and a connector 72 on the casing communicates with the chamber 70. A further hose (not shown) connects the connector 72 with the water outlet of the radiator. The pressure drop created across the gates 32a is thereby used to promote a circulation of the water between the hydraulic retarder and the radiator for the purpose of cooling the water.

Whereas the retarders of Figs. 1 to 3 of the drawings have three gates 32, the retarder of Figs. 4 and 5 has only two gates 32a, which are arranged diametrically opposite one another.

Since the hydraulic fluid is water in the embodiment of Figs. 4 and 5, the seals 74 between the casing 22 and the shaft 26 are arranged so as to isolate the bearings from the annular manifold chambers 62 and 70.

Other features of the hydraulic retarder of Figs. 4 and 5 and its mode of operation are as described with reference to Figs. 1 to 3.

Whereas the hydraulic retarders of Figs. 1 to 5 have stators 20 provided with two rows of blades 30, 31 arranged at opposite sides of the side channel or vortex chamber 24, the retarder of Fig. 6 has only one row of blades 130 and these are on the rotor 128 which is part of the casing 122 which is keyed to the shaft 126. The gates are slidably mounted in a stator core 127 but are not shown in Fig. 6. There may be three gates, as in Fig. 2, or two gates, as shown in Fig. 5. The gates are displaceable into and out of the vortex chamber 124 by means of racks which mesh with a pinion 140 on a sleeve 145 to which an adjusting lever 154 is attached. The stator core 127 forms part of a stator 120 which is prevented from rotating by means of one or more stays 121.

The vortex chamber 124 contains a hydraulic fluid which can be circulated through the engine cooling radiator, as described with reference to Figs. 4 and 5, or can be oil topped up from a reservoir, as described with reference to Figs. 1 and 2. The passagesforthe hydraulic fluid have to be led out through the stator 120, since the casing 122 rotates in this embodiment. in the case of water circulation, an annular manifold chamber 162 at one side of the stator core 127 is connected to the zones of the vortex chamber 124 in front of the gates and an annular manifold chamber 170 at the other side of the stator core 127 is connected to the zones of the vortex chamber behind the gates. Respective passages in the stator 120 connect the chambers 162 and 170 to outlet and inlet connections (not shown).

In operation, with the gates fully retracted so that their outer extremities are flush with the outer periphery 129 of the core 127, the hydraulic fluid is simply whirled round with the rotor 128 and the only resistance to rotation is the bearing friction and the skin friction at the relatively small area of the stationary outer periphery 129 of the core.

When the gates are radially extended into the vortex chamber 124 by adjusting the lever 121, the blades 130 behave as pump impeller blades and create a pressure difference across the gates, whereby the reaction due to the pumping action of the impeller blades provides the retarding torque.

The retarder of Fig. 6 can be air cooled, e.g. by radial fins 182 and/or circumferential fins 184 on the rotor 128.

A brake band 180 or brake shoe can be arranged to co-operate with the outer periphery of the rotatable casing 122 to provide mechanical braking.

The embodiment of Figure 6 could be modified to provide two rows of blades 130 at opposite sides of the vortex chamber 124, as in Figures 1 to 5, and the embodiments of Figures 1 to 5 could be modified to provide a single row of blades 30 at one side of the vortex chamber 24, as in the embodiment of Figure 6.

In the embodiment of Figure 7, the gate is moved into or out of the fluid chamber by a cranked lever 202 comprising an arm 204 carried at one end on a bearing 206 rotatable with a rotatable element such as element 42 or 43, and an arm 208 pivoted at one end to the other end of arm 204. The arm 208 is in turn pivoted at its other end to a gate; the gate in this instance having the general form of a bell-crank lever pivoted at the crank to the respective coupling part by pin 210.The crank of lever 202 is connected to one end of a compression spring 212 the other end of which is anchored on the respective coupling part, so that the spring forces the crank of lever 202 anti-clockwise to pivot one arm 214 of the gate fully into the fluid chamber to co-operate at its extremity with the facing wall of the fluid chamber, while the other arm 216 of the gate closes the gap in the respective coupling part. That gap is delimited by an arcuate surface 218 along the arc of which the arm 216 pivots. To prevent the arm 214 from being pivoted anti-clockwise from the position shown in Figure 7, a stop 220 is provided to engage arm 204 of lever 202.The gate in Figure 7 is shown in its fully extended position and is normally held there by spring 212 under a predetermined loading. Ifthe loading on arm 214 of the gate exceeds the predetermined loading, the arm deflects anticlockwise as seen in Figure 7 to the extent needed to relieve the overload on the gate.

Because the hydraulic retarders in accordance with the invention are not normally emptied of hydraulic fluid, there is no need to provide tanks or similar spaces for accommodating fluid drained from the retarder as in the scoop type hydrodynamic retarders of the prior art. This feature amongst others enables the hydraulic retarders according to the invention to be made much smaller than prior art hydrodynamic retarders of a similar performance. This is of great advantage when installation space is limited as in the case of mechanically propelled vehicles fitted with retarders. Also the substantially instantaneous response upon adjustment of the gates compares favourably with the delay encountered by the filling and emptying of the prior art retarders.

Claims (20)

1. An hydraulic coupling suitable for use also as an hydraulic retarder; the coupling being ofthe kind employing the principle of a centrifugal side channel high pressure pump designed for zero delivery and comprising relatively rotating parts housed within a casing and defining an annular fluid chamber between them filled with hydraulic fluid, one of the parts having radial vanes thereon and the other part having at least one gate displaceable into the fluid chamber, characterised in that the or each gate (32) can be withdrawn completely from the fluid chamber (24) to leave the latter substantially unobstructed and in that the coupling provides means (38, 40,42,44,46,48, 50) operable externally of said casing for varying the extent to which the gate is displaced into the chamber; whereby, when the or each gate (32) is fully withdrawn from the fluid chamber (24) to operate the coupling at zero delivery there is no bodily movement of the hydraulic fluid relative to the vaned part (20) thereby reducing energy dissipation in the coupling to a minimum; and whereby, when the or each gate (32) is displaced into the fluid chamber, the delivery of the coupling can be controlled by operation of said means (38,40,42,44,46,48,50).

2. A coupling according to Claim 1,wherein said means (38,40,42,44,46,48, 50) are such that the or each gate (32) can be infinitely adjusted between the position in which the or each gate is fully displaced into the fluid chamber and the fully retracted position.

3. A coupling according to Claim 1 or 2, wherein said means (38,40,42, 44,46, 48, 50) comprises an angularly displaceable member (42) to act on the or each gate (32) and the or each gate (32) is such as to be displaceable on angular displacement of said member (42).

4. A coupling according to Claim 3, wherein said member (42) is relatively rotatably mounted but non-axially displaceably mounted on a shaft (26) carrying said other part (28) of the coupling, and said means (38, 40, 42, 44,46,48, 50) further comprises an input sleeve (44) axially displaceable but non-relatively rotatably mounted on said shaft (26), and a helical connection (46,48) provided between the sleeve (44) and the member (42), whereby axial displacement of the sleeve (44) causes said member (42) to be angularly displaced relative to the shaft (26).

5. A retarder or coupling according to Claim 4, wherein the helical connection (46,48) has a helix angle such that the sleeve (44) can displace the gate or gates (32) but the gate or gates (32) cannot displace the sleeve (44).

6. A coupling according to Claim 3, wherein said means further comprises a differential mechanism (47) such that an angular displacement of an input sleeve (45) thereof relative to the non-rotatable part (20) causes a corresponding angular displacement of said member (42) relative to the rotatable part (28) irrespective of the speed of rotation of the rotatable part (28).

7. A coupling according to Claim 6, wherein the differential mechanism (47) comprises double differential gear train (49,51,53).

8. A coupling according to any of the preceding Claims 3 to 7, wherein the gate or gates (32) comprise a rack (38) and said member (42) comprises a pinion (40) meshing with the rack (38) of a gate (32).

9. A coupling according to Claim 8, wherein, in the case where more than one gate is employed, said means (38,40,42, 44,46,48, 50) comprises one pinion (40) meshing with the rack (38) of each gate.

10. A coupling according to any of Claims 1 to 7, wherein the gate or each gate (32) is mounted to pivot into and out of the fluid chamber and means (207,204,206,208,212) are provided to bias the gate or gates into the chamber, whereby in the event of an overload of hydraulic fluid acting on the gate or gates in a direction opposed to that in which the or each gate pivots into the chamber, the or each gate pivots against the biasing means to increase the fluid size of the fluid passageway past the gate or gates and thereby to relieve the overload.

11. A coupling according to any of the preceding claims for use as a retarder, wherein one (20) of the parts is non-rotatable and the part (28) having the movable gate or gates is the rotatable part.

12. A coupling according to any of preceding Claims 1 to 10, for use as a retarder, wherein one (127) of the parts is non-rotatable and constitutes the part having the core and the movable gate or gates.

13. A coupling according to Claim 11 or 12, for use as a retarder, comprising coolant passages (21, 23) associated with the non-rotatable part of cooling the hydraulic fluid.

14. A coupling according to Claim 11 or 12, comprising passage means (60, 62, 66, 68,70, 72) to permit connection of the coupling to a cooling system of apparatus to which the coupling is in use fitted, whereby the coolant of the cooling system is employed as the hydraulic fluid.

15. A coupling according to any of the preceding Claims, comprising two gates.

16. A coupling according to any preceding Claims 1 to 14, comprising three or four gates.

17. A coupling according to any of the preceding Claims, wherein said fluid chamber (24) defined by said relatively rotating parts is delimited by said casing (22, 122).

18. A coupling according to Claim 17, wherein said one part (20,128) having radial vanes thereon is integral with the casing (22,122).

19. A coupling according to Claim 17, wherein said other part (28, 120) having at least one gate is integral with the casing (22, 122).

20. An hydraulic coupling substantially as hereinbefore described with reference to Figures 1 and 2, or Figure 3 or Figures 4 and 5 or Figure 6 or Figure 7 of the accompanying drawings.