US3385061A

US3385061A - Formation of the circuit in hydrodynamic torque converters

Info

Publication number: US3385061A
Application number: US558799A
Authority: US
Inventors: Lysholm Alf
Original assignee: Individual
Current assignee: Individual
Priority date: 1965-06-28
Filing date: 1966-06-20
Publication date: 1968-05-28
Anticipated expiration: 1985-05-28
Also published as: DE1550756B1; NL146584B; CH492145A; BE683271A; GB1153873A; NL6608955A

Description

May 28, 1968 l A. LYSHOLM 3,335,061

FORMATION OF THE CIRCUIT IN HYDRODYNAMIC TORQUE CONVERTERS Filed June 20, 1966 2 Sheets-Sheet 1 L V E 2 1 23- v A 1-3- )18 1 28 -19 L Q zzmvrozz. i\\\\\\\\ 1 BY; W

y 28, 1958 A. LYSHOLM 3,385,061

FORMATION OF THE CIRCUIT IN HYDRODYNAMIC TORQUE CONVERTERS Filed June 20, 1966 2 Sheets-Sheet 2 VFIG.Z.

fix 1g VEN TOR. Mm, rauv United States Patent 3,385,061 FORMATION OF THE CIRCUIT IN HYDRO- DYNAMIC TORQUE CONVERTERS Alf Lysholm, Karlaplan 11, Stockholm, Sweden Filed June 20, 1966, Ser. No. 558,799 Claims priority, application Sweden, June 28, 1965, 8,483/65 5 Claims. (Cl. 60-54) ABSTRACT OF THE DISCLOSURE Flow losses in a hydrodynamic torque converter are reduced by providing an improved configuration for an inner bend of a torus-shaped working chamber in the converter. The through-flow area of the inner bend of a working chamber circuit is formed with a successively increasing restriction of at least 5% in order to obtain a maximum restriction ahead of the impeller entrance at a certain radial section of the inner bend. Also, a sealing slot may be formed between a portion of a curved reaction blade ring and an adjacent impeller blade ring to reduce flow separation by a Coanda effect produced by leaking current through the sealing slot.

This invention relates to hydrodynamic torque converters having a toric hydraulic working chamber in which impeller blades, turbine blades and reactor blades are arranged in a conventional manner, and the object of the invention is to reduce the flow losses by suitable formation of the radially inner bend of the working chamber.

In torque converters of this kind the rotatably mounted impeller receives mechanical energy from an engine. In the working chamber this energy is partly converted into hydraulic energy due to the fact that the impeller blades impart an increased head to a hydraulic fluid confined in the working chamber at superatmospheric pressure and due to the fact that the hydraulic fluid is positively circulated in the working chamber.

As a result the fluid is caused to flow through the turbine and imparts rotation to a turbine disc that carries the turbine blades. The turbine disc is connected to a turbine shaft which may be the output shaft of the transmission.

The reactor or stator blades are either secured to a single stationary member or divided into a group secured to a stationary member and a group secured to a freely rotatable member. In both cases the stationary reactor stabilizes the flow at high speed ratios.

In the above named type of torque converters a great amount of circulating liquid is of high importance and, therefore endeavours are made to reduce the flow losses by suitable choice of the number of blades in the members of the converter and by suitable design of the protiles and angles of the blades and of the toric circuit.

For this purpose it is known to reduce the blade losses and shock losses of the torque converter by forming both the turbine blades and the liquid-guiding reactor blades with different thicknesses at the entrance and exit edges and by the provision of favourable aspect ratios and pitch ratios, the aspect ratio being the ratio of the length to the width of the blade and the pitch ratio being the ratio of the blade pitch to the width of the blade.

In hydrodynamic torque converters characterized by a high stall torque at a flat efiiciency curve within the possible speed range it is common practice to provide no blades in the radially outer and radially inner bend of the toric circuit so that the bends are in the form of passages for free flow of the hydraulic fluid. The cross-section of the flow in such bends is defined by an inner core ring carried by the reactor or turbine and by the internal toric surface of the working chamber. In prior-art constructions this cross-section is substantially throughout constant.

'ice

Yet it is known to devise the bends in consideration such that they are first diverging from the entrance and then converging toward the exit thereof with the maximum cross-sectional area located midway between the entrance and exit. Further, theories have been presented claiming that the formation of the radially inner bend of the working chamber relative to the outer bend is of minor importance because of the fact that the velocity components of the flow through the inner bend, f.i. between the reactor exit and the impeller entrance, are counteracting each other so as to reduce the risk of flow separation. There is no doubt that such reasoning is justified, but recent flow measurements have proved that with conventional cross-sectional areas of the inner bend of the circuit a considerable flow separation nevertheless occurs especially along the inner radius at the impeller entrance with the result of flow losses of the order of 2% The present invention has for its object to reduce the above mentioned flow losses by a proper form of the torus-shaped working chamber of a hydrodynamic torque converter. In said working chamber an impeller blade ring is provided for rotation and for radial outward flow of the hydraulic working fluid. One or more turbine blade rings are also provided in said working chamber and one or more reactor blade rings are alternatively provided for radial outward flow and/ or radial inward flow, said blade rings forming radially inwardly and outwardly directed flow channels, which are connected to an outer and an inner bladeless bend to form a closed transverse circuit of the working chamber. The outer boundary surface of this circuit is obtained by a combined cooperation between the internal surface of a casing surrounding the working chamber and by the hubs of the blade rings. The inner boundary surface of the circuit is formed by the respective inner rings of the blade rings which are provided to fit into and to each other to form a central core ring in the working chamber. The hydrodynamic torque converter of the kind referred to above is according to the invention'substantially characterized in that the through-flow area of the inner bend of the circuit seen in the direction of flow is formed with a successively increasing restriction of at least 5% in order to obtain the maximum restriction ahead of the impeller entrance in a cross-sectional radial relative to the boundary surface of the impeller entrance and taken through the edge of the core ring where the inner peripheral guidance for the inner ring of the reactor blade ring terminates. The starting place of said restriction lies within the range of two thirds of the length of flow between the entrance and the exit of said bend. The through-flow area along the length of flow between the entrance of the bend and the starting place of the restriction is preferably constant.

As a result of the form of the working chamber according to the invention the speed of the working fluid is increased upon the flow through the nozzle-like restriction of the inner bend which has shown advantageous in order to prevent a flow separation and which has further resulted in that torque converters having a working chamber formed according to the invention have a higher efficiency and a wider working range than torque converters having a conventional form of the working chamber.

The invention may be applied to any kind of working chamber of a hydrodynamic torque converter and to this end the invention is further characterized in that in such cases where the radial inward flow channel which is by less than 8% greater than the through-flow area of the impeller entrance, the through-flow area of the entrance downstream the maximum restriction seen in the flow direction and immediately ahead of the impeller entrance is formed with a small shoulder-like widening which causes a flow separation and effects a Carnot shock and as a result thereof a moderate vortex. This vortex reestablishes a thin boundary layer at the impeller entrance and improves the flow in the impeller blade ring. Due to the small widening the losses due to the Carnot shock will be small (about 0.1%

The hydrodynamic torque converter according to the invention is further characterized in that a sealing slot may be provided between the radially inner edge of the inner ring of the impeller blade ring and the radially inner surface of a recess formed in the inner ring of the reactor blade ring, said sealing slot being so shaped that it will be possible to utilize the leaking current in order to obtain a Coanda effect, i.e. a reduction of the boundary layer so that the boundary layer along the inner sides of the impeller blades will become thinner and flow separation will be counter-acted.

A hydrodynamic torque converter according to the invention will be described more in detail with reference to the annexed drawings showing suitable embodiments for a single-stage, two phase and double rotation type, respectively, FIGS. 1 to 3 illustrating axial longitudinal sectional views of one-half of the various working chamber of the respective torque converters.

Referring to the embodiment of the Single stage converter illustrated in FIG. 1 more than half of the external boundary of the working chamber is defined by the internal surface of a two

part casing

10, 1b which in a manner not shown is secured to the support of the torque converter. The remaining external boundary surface of the working chamber is formed by the hub of an impeller 2 and by an outer lateral ring 3b of a set of turbine blades 3a.

Secured to the half 1a of the casing is a set of reactor blades 4a the inner ends of which are connected to and, carry a core ring 5. On the side remote from the reactor blades 4a the core ring has a recess 5a in which both an inner lateral ring 3c for the turbine blades 3a and an inner ring 2c for the blades 2a of the impeller 2 are rotatably disposed and smoothly merge into the external surface of the core ring 5.

The impeller 2 is by means of splines or the like secured on a tubular shaft 6 which by means of a ball bearing 7 in the half 1a of the casing and by means of a journal bearing 8 or the like in a turbine disc 3 is rotatably mounted for transmitting mechanical energy from an engine, not shown, to the torque converter.

The impeller blades 2a impart circulating motion to a hydraulic fluid which at superatmospheric pressure is confined in the working chamber. The liquid flows through the set of turbine blades 3a so as to impart rotation to the turbine wheel 3. This turbine wheel 3 is formed with a turbine shaft 3d which is rotatably mounted in a ball bearing 9 in the half 1b of the casing and is the output shaft of the transmission.

In a working chamber formed as described above the joining

external boundary surfaces

1b, 2b, 3b and the core ring 5 together with the joining inner rings 2c, 30 for the

blades

2a, 3a define a circuit for the hydraulic fluid, said circuit comprising a radial outward flow passage 10 and a corresponding inward flow passage 11 communicating with each other through an outer and an inner

bladeless bend

12 and 13, respectively.

As mentioned above, the impeller blades 2a and the turbine blades 3a are rotatably disposed in the outward flow passage 10, whereas the stator or reactor blades 4a which deflect the liquid in a certain direction are stationarily mounted in the inward flow passage 11. The location of the turbine blades 3a radially outwardly of, and in immediate succession after the impeller blades 2a as viewed in the direction of flow, renders possible effective utilization of the various velocity components from the impeller exit for torque conversion.

In the embodiment illustrated in FIG. 1 the cross-sectional area of the inward flow passage 11 of the circuit is slightly greater than the cross-sectional area of the outward flow passage 10, and the cross-sectional area of the outer connecting bend 12 is substantially constant. Tests have proved, however, that it is possible, in order to reduce the external diameter of the

casing

1a, 1b to reduce the cross-sectional area by about 10% midway of the bend 12 without the occurence of additional losses.

In contrast thereto the inner connecting bend 13 between the inward fiow passage and the outward flow passage is much more sensitive as regards its formation for preventing flow separation along its inner radius. For this reason the inner bend 13 is formed in accordance with the invention with a nozzle-like restriction of at least 5%, the maximum restriction being located at a section AA extending radially of the boundary sur faces and through the edge of the core ring 5 where the peripheral guidance at the inner radius of the recess 5a terminates. The starting place of the restriction may vary within the range of two thirds of the length of flow between the entrance and exit of the bend 13.

In the embodiment shown in FIG. 1 the starting place of the restriction is such that the length of the restricted portion is the minimum length according to the invention, the cross-sectional area of the bend 13 being substantially constant along two thirds of the length of the bend, and the succeeding gradual restriction is obtained by a suitable form of the hub of the impeller wheel 2.

If the inward flow passage 11 is not by more than 5% greater than the outward flow passage 10 the area of the maximum restriction is less than the area at the impeller entrance. In order to prevent flow separation at the impeller entrance, a shoulder-like widening 2b of the crosssectional area is formed in the hub of the propeller 2. The abrupt widening 2b causes separation at the outer boundary and a Carnot shock with a resultant moderate vortex which reestablishes a thin boundary layer at the layer at the impeller entrance.

Such a widening 2b is not confined to the above indicated area ratio of the inward to the outward flow passage, but can advantageously be applied even in case of greater percentage differences between the cross-sectional areas of the inward and outward flow passages.

Along the inner radius flow separating at the impeller entrance is counteracted due to the fact that a sealing slot between the inner radial edge of the inner ring 2c of the impeller and an internal projecting surface of the core ring 5 is devised such that the leaking current can be used to produce a Coanda effect or boundary layer reduction. This may be effected for instance :by forming the internal surface of the core ring 5 with an angular projection 5b which together with the inner ring 20 of the impeller defines a desired sealing slot by forming the curvature of the inner side of the inner ring 2c that faces the impeller blades such as to cause the leaking current to flow radially outward along the ring 20. The leaking current has a high velocity and therefore assists in making the boundary layer thinner and in counteracting flow separation along the inner side of the impeller blades 2a.

The formation of a hydraulic working chamber according to the invention as applied to a torque converter of the two-phase type is shown in FIG. 2 in which the gradually restricted portion of the inner bend 13 of the circuit is of maximum length within the scope of the invention. Here the cross-sectional area of the inward flow passage 11 is by less than 8% greater than that of the outward flow passage, and even in this case a shoulderlike widening 2b of the flow passage is formed in the hub of the impeller wheel 2 immediately ahead of the impeller entrance.

Similarly to the single-stage converter according to FIG. 1 the impeller blades 2a and the turbine blades 3a are located in the outward flow passage 10 of the circuit and mechanical energy is similarly transmitted by the impeller 2 and taken out via the turbine wheel 3. The bearings for the impeller and the turbine and the location of their inner rings 20, 30 relative to the external surface of the central core ring 5 are the same as in the single-stage converter. In contrast thereto the internal surface of the

stationary casing

1a, 1b ofthe working chamber forms only the outer boundary of the outer bend 12 of the working chamber. In the two-phase converter according to FIG. 2 the outer boundary of the inward flow passage 11 and the first quadrant of the inner :bend 13 in the direction of flow are formed by the hubs of two

reactor wheels

24, 25.

Thereactor wheel 24 is stationarily mounted in the

casing

1a, 1b and carries a set of fixed reactor blades 24a located substantially at the same radius as the impeller blades 2a. Similarly to the previous embodiment the reactor blades 24a are connected to and support the core ring 5.

The reactor wheel 25, the blades 25a of which are located radially outside the reactor blades 24a is mounted for rotation via a free wheel 14 as previously known in two-phase converters. The free wheel prevents relative rotation of the reactor wheel 25 counter to the impeller wheel 2 and turbine wheel 3, for instance during the start. At higher speed ratios the reactor blades 25a are subjected to forces opposite to the forces acting during the start resulting in that the reactor wheel 25 will be entrained and rotate freely in the liquid current without producing reaction. It is therefore especially import-ant to reduce the flow losses in the reactor 25a by suitable design of these reactor blades as to curvature as well as thickness.

In the embodiment illustrated an inner ring 250 which interconnects the reactor blades 25a of the upper reactor fits a recess in the fixed core ring 5 and merges smoothly into the outer boundary surface of the core.

The engagement and disengagement of the upper reactor blades 25a as an indirect function of the speed ratio of the engine and the adaptation of the torque converter to alternative gear ratios in combination with a difierential gear or the like form no part of the invention and are not described in this connection.

The blade system used in two-phase converters can advantageously also be used in torque converters of the counter rotation type. As shown in FIG. 3 the upper reactor blades 16a are in this case secured to one half a of a two-part fcasing which encloses the working chamber. One end wall 15a of the casing is mounted for rotation in a central journal bearing 28 and the other end wall 15b is rigidly connected to a ring gear 17 of a planetary gearing. The planet gears 18 are rotatably mounted on shafts 19 which are secured to a stationary casing 20 surrounding the torque converter. The sun gear 21 of the planetary gearing is movably mounted on the output shaft 3d of the turbine wheel and cooperates with said shaft via a free-wheeling unit 22.

During backward rotation of the upper reactor blades 16a under reaction of the flow of fluid a corresponding torque is produced which via the

casing

15a, 15b is transmitted to the planetary gearing which reverses the direction of the torque and via the free-Wheel 22 transmits the torque to the output shaft 3d of the transmission. In this way the torque of the upper reactor blades 16 is added to the output torque of the turbine Wheel resulting in a considerable torque multiplication. The described counter rotation torque converter is distinguished 'by a high stall torque and by a high efiiciency at high speed ratios.

In counter rotation torque converters it is possible to displace the efiiciency curve by transmitting the torque of the upper reactor blades 16 to the sun gear 21 of the planetary gear in which case the cooperating torques are taken out at the ring gear 17. Such modification need not be described in this connection.

The cross-sectional area of the circuit of the embodiment shown in FIG. 3 is defined in the outer part of the circuit in the same manner as in the two-phase converter, whereas the inner boundary surface of the circuit which may have a fixed core ring in accordance with FIG. 2 consists of two parts in the counter rotation type illustrated. The lower ring part 23 is secured to the stationary reactor blades 26a and the upper part 27 is in the form of an inner connection ring for the upper reactor blades 16a.

In the embodiment illustrated in FIG. 3 the cross-sectional area at the impeller entrance is only of the cross-sectional area at the reactor exit. For this reason the widening 2b of the cross-sectional area immediately ahead of the impeller blades 2a shown in FIGS. 1 and 2 is not necessary in this embodiment. The cross-sectional area of the inner bend 13 is constant along two thirds of the length of flow between the reactor exit and the impeller entrance and is equal to the cross-sectional area at the reactor exit. After two thirds of the length of flow the hub of the impeller wheel 2 is formed such that the cross-sectional area will be gradually restricted to the maximum restriction AA previously defined in this description. The cross-sectional area at the place of maximum restriction is reduced to the corresponding area at the impeller entrance, and the portion between the maximum restriction at the impeller entrance is substantially of constant cross-sectional area.

What I claim is:

1. A hydrodynamic torque converter having a torusshaped working chamber for a hydraulic working fluid, an impeller blade ring (2a) being provided in said chamber for rotation therein and being provided for effecting a radial outward flow of the working fluid, at least one turbine blade ring (3a) and at least one reactor blade ring (4a and 24a, 16a, 26a, respectively) being provided in said chamber alternatively for radial outward flow and/ or for radial inward flow, said blade rings forming radially inwardly and outwardly directed flow channels (10 and 11) which are connected to an outer and an inner bladeless bend (12 and 13, respectively) to form a closed transverse circuit of the working chamber, said circuit having an outer boundary surface obtained by a combined cooperation between the internal surface of a casing (1a, 1b and 15a, 1512, respectively) surrounding the working chamber and of the hubs of the blade rings, the inner boundary surface of said circuit being formed by the respective inner rings 2c, 30, 5 and 5, 25c and 23, 27, respectively) of the blade rings, said inner rings being provided to fit into and to each other for forming of a central core in the working chamber, characterized in that the through-flow area of the inner bend (13) of the circuit seen in the direction of flow is formed with a successively increasing restriction of at least 5% in order to obtain the maximum restriction ahead of the impeller entrance in a section (AA) radial relative to the boundary surfaces of the impeller entrance and taken through the edge of the core ring where the inner peripheral guidance for the inner ring (5 and 23, respectively) of the reactor blade ring terminates, and in that the starting place of the restriction lies within a range of two-thirds of the length of flow between the entrance and exit of said bend (13), the through-flow area along the length of flow between the entrance of the bend (13) and the starting place of the restricted portion being preferably constant.

2. A torque converter according to claim 1, characterized in that a sealing slot is provided between the radially inner edge of the impeller blade rin and the radially inner surface of a recess (5a) formed in the inner ring of the reactor blade ring, said sealing slot being so formed that it will be possible to utilize the leaking current to obtain a so called Coanda eifect, i.e. a reduction of the boundary layer so that the boundary layer along the inner sides of the impeller blades 2a) will become thinner and flow separation will be counteracted.

3. A torque converter according to claim 1, characterized in that the internal surface of a recess (5a) in the inner ring of the reactor blade ring is formed with a cam (5b) and in that the inner ring (20) of the impeller blade ring is adapted to fit to said recess in such a way as to give a desired sealing slot, the radially inner edge of the inner ring against the impeller blades having a curvedshape which guides the leaking current to follow the ring (20) radially outwardly.

4. A torque converter according to claim 1, characterized in that in case the inward flow channel (11) has a through-flow area which is by less than 8% greater than the through-flow area of the impeller entrance, the through-flow area of the entrance downstream the maximum restriction (A-A) seen in the flow direction and immediately ahead of the impeller entrance is formed 10 with a small shoulder-like widening (2b) which causes a Carnot shock with a moderate vortex which reestablishes a thin boundary layer at the impeller entrance.

8 5. A torque converter according to claim 1, characterized in that the shoulder-like widening (2b) of the through-flow area is formed in the hub of the impeller (2).

References Cited UNITED STATES PATENTS 3,016,709 1/1962 Lyshom 60-54 3,071,928 1/1963 Dundore et a1. 60-54 3,105,396 10/1963 Dundore et a1 6064 XR EDGAR W. GEOGHEGAN, Primary Examiner.