WO1986002132A1 - Viscous clutch with filling adjustment - Google Patents

Abstract

A viscous clutch for use as an engaging clutch for a vehicle differential gear system, with a working chamber (4) and a storage chamber (5). A pump (6, 7, 8) supplies liquid from the storage chamber (5) into the working chamber (4). When a pre-set relative rotation speed is exceeded, first valve (3, 12) closes a first return flow line (19, 20); when a pre-set temperature is exceeded a second valve (12, 31) opens a second return line (32, 36) from the working chamber (4) to the storage chamber (5). The torque and heat loss of the viscous clutch are low at a low relative rotation speed and/or high temperature. The torque is large only when the valves simultaneously exceed a pre-set relative rotation speed and fall below a pre-set temperature.

Description

 Viscous coupling with filling control

The invention relates to a viscous coupling according to the preamble of the main claim.

A viscous coupling of this type is known (DE-PS 21 35 791).

A viscous clutch according to DE-PS 21 35 791 has a torque that increases with increasing relative speed. A small viscous clutch of this type still allows almost free speed compensation when cornering on a rough road. A large such viscous coupling generates a large locking torque when a wheel wants to spin due to insufficient frictional contact with the ground and thus secures the wheel or - in the case of more than two driven wheels - the wheels on grippy ground even in extreme cases the necessary drive torque. A conventional medium-sized viscous coupling of this kind hinders the speed compensation when cornering and generates only a limited locking torque. This results in increased tire wear and increased steering forces, lost power and increased fuel consumption when cornering on a grippy road. As a result, when a wheel spins, the drive torque on the still gripping wheel or - in the case of more than two driven wheels - on the still gripping wheels in extreme driving conditions is no longer sufficient to secure the drive of the vehicle.

The invention has for its object to provide a viscous coupling according to the preamble of the main claim, which both allows an almost free speed compensation when cornering on a grippy roadway and also generates a very large locking torque when a wheel wants to spin due to poor frictional contact with the ground . This task is accomplished with the characterizing features of the main claim. While at low relative speeds, such as occur when cornering on a non-slip road, the working chamber of the viscous coupling contains only a small amount of liquid and therefore only a small locking torque is created, which hardly impedes the speed compensation, the pump effects at higher relative speeds, such as when spinning of a wheel arise that the working chamber is filled to overflow and the viscous coupling thus generates a very large locking torque.

Claim 2 specifies a particularly simple design of a pump. A pump of this type is known per se (DE-PS 12 84 186, DE-PS 30 09 665), but not in connection with a viscose coupling according to the main claim.

Claim 3 adds the advantage that the amount of liquid in the working chamber and thus the torque of the viscous clutch are even more reliably low below a predetermined relative speed and very large above this relative speed. The transition from a low torque, which hardly impedes the speed compensation when cornering, to a large torque, which greatly limits the speed compensation and thus secures the drive of the vehicle and vice versa, occurs at a relative speed just above a highest value, that when cornering can still occur within a small relative speed range.

Claim 4 adds features with which the relative speed shut-off valve according to claim 3 can be designed to save space with particularly simple components.

Claim 5 adds features with which overheating and thus damage to the viscous coupling is prevented. Thermal shut-off valves for regulating the amount of liquid in a working Chamber and thus for regulating the torque of a viscous coupling are known per se (DE-PS 12 84 186), but not in connection with a viscous coupling according to the main claim.

Claim 6 adds features with which the thermal shut-off valve can be represented with only a few, simple, additional components.

Claim 7 adds a feature with which the bimetal cantilever is protected particularly reliably against permanent deformation.

Claim 8 has the advantage that an additional cantilever spring is omitted.

Claim 9 has the advantage that the function of the thermal shut-off valve is not influenced by liquid friction forces occurring at relative speed.

Claim 10 has the advantage that the function of the thermal shut-off valve is not disturbed by the pressure drop between the two chambers.

In the drawing, an embodiment of a viscose coupling according to the invention is shown. It shows

Fig. 1 shows a cross section, Fig. 2 shows a longitudinal section, Fig. 3 shows a longitudinal section.

A first assembly 1 and a second assembly 2 form a housing 1, 2 partially filled with a liquid. An intermediate wall 3 is firmly connected to the first assembly 1 and divides the housing 1, 2 into a working chamber 4 and a storage chamber 5. A pump rotor 6 is arranged in the storage chamber 5 and firmly connected to the second assembly 2. Close to her Ren edge carries the partition 3 bluff body 7, which protrude axially into the storage chamber 5. In the circumferential direction on both sides of the bluff body 7, the intermediate wall 3 has discharge openings 8. At a relative speed between the assembly 1 and the assembly 2, the pump rotor 6, the bluff bodies 7 and the discharge openings 8 act together as pumps 6, 7, 8 and convey liquid from the storage chamber 5 into the working chamber 4. With the inner wall of the intermediate wall 3 carries a bearing ring 9 and on this bearing ring 9 a bearing washer 10, a corrugated ring spring 11 and a washer 12. The corrugated ring spring 11 presses the washer 12 axially against the intermediate wall 3. The washer 12 is to the intermediate wall 3 rotatable, delimited by a rivet pin 13 on the intermediate wall 3 in a window 14 of the disk 12. A circular ring leg spring 15, guided in a central region by a hook 16 on the disk 12, with its legs 17 pointing radially outwards on the rivet pin 13 and / or an axial web 18 of the disk 12, acts as a return spring 15 and holds the disk 12 in a middle, first position, in the first diameter, relative to the intermediate wall 3 Breaks 19, 20 in the form of radial slots 19, 20 in the intermediate wall 3 and in the disk 12 form an open return line 19, 20 through which liquid flows back from the working chamber 4 into the storage chamber 5.

A cover disk 22 is firmly connected to the disk 12 via support rivets 21. Arranged axially next to the cover plate 22, a drag plate 23 is rotatably connected to the second assembly 2. At a relative speed between the first assembly 1 and the second assembly 2, liquid generates a drag torque on the cover disk 22 in a narrow gap 24 between the drag disk 23 and the cover disk 22 and on the disk 12 via the support rivets 21 increasing relative speed greater than a holding torque by a biasing force of the return spring 15, the disc 12 rotates relative to the intermediate wall 3 into a second position, in which webs 37 between the slots 19 of the intermediate wall 3 Slots 20 of the ^'disc 12 and webs 25 of the disk 12 of the partition wall 3 close between the slots 20, the slots 19 with flat sealing surfaces 26, a through the partition 3 and the disc 12 formed relative speed cutoff valve 3, 12 is thus closed and fluid only still flows back through an overflow opening 27 radially inside the bearing ring 9 from the working chamber 4 into the storage chamber 5.

The pump 6, 7, 8 and the relative speed shut-off valve 3, 12 together have the effect that the working chamber 4 of the viscose coupling contains only a small amount of liquid at low relative speeds and the viscous coupling generates only a very small torque, so that when exceeded a predetermined relative speed, the amount of liquid in the working chamber 4 rises and the viscous coupling thus achieves a very large torque, and that when the value falls below this predetermined relative speed, the amount of liquid in the working chamber 4 decreases again and the torque of the viscous coupling becomes very low again.

28 cantilever springs 29 and bimetallic cantilever bars 30 are fastened to the disk 12 with rivets. The cantilever springs 29 form with their free end 31 closing members 31 which, with a slight pretension of the cantilever springs 29, close second openings 32 in the disk 12 in a first position. The free end 31 of the cantilever spring 29 carries a hook-shaped extension 33. The free end 34 of the bimetallic cantilever rods 30 protrude into a space 35 between the extension 33 and the free end 31 of the cantilever spring 29.

When a predetermined temperature is exceeded, the bimetallic cantilever 30 bends as a thermal expansion element 30, its free end 34 grips the extension 33, thus lifts the free end 31 of the cantilever spring 29 as a closing element 31 from the opening 32 in the disk 12 and forms the second Breakthroughs 32 in the Disc 12 together with second openings 36 in the intermediate wall 3 open return lines 32, 36 through which liquid flows back from the working chamber 4 into the storage chamber 5.

When the temperature falls below this predetermined temperature, the bimetallic cantilever rod 30 extends again, its free end 34 releases the extension 33 again, the free end 31 of the cantilever spring 29 closes the opening 32 and thus the second return line 32, 36, the amount of liquid in the working chamber 4 and thus the torque of the viscous clutch rise again.

The free end 31 of the cantilever spring 29 and the disk 12 thus form a thermal shut-off valve 12, 31.

The relative speed blocking valve 3, 12 with first return lines 19, 20 and the thermal blocking valve 12, 31 with second return lines 32, 36 open and close independently of one another. The amount of liquid increases only when both the relative speed blocking valve 3, 12 and the thermal blocking valve 12, 31 are closed, and only when a predetermined relative speed is exceeded and a predetermined temperature is undershot the working chamber 4 to overflow through the overflow opening 27, the viscous coupling generates a large locking torque. If even one of the two valves 3, 12 or 12, 31 is open, the amount of liquid in the working chamber 4 and thus the torque of the viscous coupling remains low. - -

Reference numerals

1 first assembly 31 second closing element,

2 second assembly free end

3 partition 32 second breakthrough,

4 working chamber, chamber second return line

5 pantry, chamber 33 extension

6 pump rotor 34 free end

7 bluff body 35 space

8 trigger opening 36 second opening,

9 bearing ring second return line

10 bearing washer 37 web

11 corrugated ring spring

12 (first) closing element, disc

13 rivet pins

14 windows

15 return spring, circular ring leg spring

16 hooks

17 legs

18 bridge

19 first breakthrough, slot, first return line

20 first breakthrough, slot, first return line

21 support rivet

22 cover plate

23 drag disc

24 gap

25 bridge

26 sealing surface

27 overflow opening

28 rivet

29 Cantilever spring, return spring

30 Bimetal cantilever

Claims

Viscous coupling with charge control 1. viscous clutch as a locking clutch for motor vehicle differential gear, with a first assembly with at least a first work surface, with a second assembly with at least a second work surface, which assemblies form a housing with a liquid, which liquid in a narrow gap between the work surfaces at a Relative speed generates an increasing torque between the assemblies with increasing relative speed, characterized in that an intermediate wall (3) places the housing (1, 2) in a work chamber (4) with the work surfaces and in a supply chamber mer (5) divides, a pump (6, 7, 8) arranged in the housing (1, 2) at a relative speed promotes liquid from the storage chamber (5) into the working chamber (4). 2. viscous coupling according to claim 1, characterized in that the pump (6, 7, 8) is a bluff body pump (6, 7, 8). 3. viscous coupling according to claim 1 or 2, characterized ge ¬ indicates that a first return line (19, 20) connects the two chambers (4, 5) radially on the outside, the intermediate wall (3) with the first assembly (1) is connected, a drag disc (23) is connected to the second assembly (2). 4th axially between the intermediate wall (3) and the drag disc (23) there is arranged a first closing member (12) which can be rotated to a limited extent to the intermediate wall (3), a return spring (15) arranged between the intermediate wall (3) and the closing member (12) holds the closing member (12) in a first position, in which the closing member (12) leaves the return line (19, 20) open, which from the pump (6, 7, 8) from the storage chamber (5) into the working chamber Mer (4) pumped liquid flows through the return line (19, 20) back into the storage chamber (5), the working chamber (4) contains only a small amount of liquid and the torque of the viscous coupling remains low, a liquid friction force of a liquid in one Narrow gap (24) between the drag disc (23) and the closing member (12) when a predetermined relative speed is exceeded against a force of the return spring (15), the closing member (12) moves into a second position in which the closing member (12) returns Line (19, 20) closes, the pump (6, 7, 8) fills the working chamber (4) up to overflow through a radially inner overflow opening (27) in the intermediate wall (3) and the torque of the viscous clutch is increased to a large one Value increases, the closing member (12) is thus an element of a relative speed check valve (3, 12). 4. viscous coupling according to claim 3, characterized ¬ characterized in that the closing member (12) to the intermediate wall (3) concentrically mounted disc (12), the disc (12) and the intermediate wall (3), seen in the axial direction having congruent first openings (19, 20) in the form of radial slots (19, 20) distributed radially on the outside on a circumferential line, with webs (25, 37) between the slots (19, 20), $ 1 in the first position of the disc (12) the slots (19, 20) form a system of parallel return lines (19, 20) with a large flow cross section overall, in the second position of the disc (12) the webs (25) of the disc (12), the slots (19) of the partition (3) and / or the webs (37) of the partition (3) close the slots (20) of the disc (12) with flat sealing surfaces (26). 5. Viscous coupling according to one of the preceding claims, characterized in that a second return line (32, 36) connects the two chambers (4, 5) radially on the outside to one another, a temperature in the viscous coupling via a thermal expansion element (30) Thermal actuating path generated with a thermal actuating force, the thermal actuating force moves a second closing element (31) against the force of a return spring (29), the closing element (31) closes the return line (32, 36) when the temperature falls below a predetermined value and when a predetermined temperature is exceeded, the closing member (31) is thus an element (31) of a thermal shut-off valve (12, 31). 6. viscous coupling according to claim 5, characterized ¬ characterized in that the disc (12) and the intermediate wall (3) have second breakthroughs (32, 36) which are so large and assigned to each other that they in each Position of the disc (12) relative to the intermediate wall (3) form the second return line (32, 36), which can only be closed by the second closing element (31), a bimetal fastened to the disc (12). Cantilever rod (30) forms the thermal expansion element (30), a cantilever spring (29) attached to the disc (12) forms the second closing element (31) with a free end (31). n in a first position of the thermal shut-off valve (31, 32), when the temperature falls below a predetermined value, the second closing member (31) with a slight pretensioning force of the cantilever spring (29) the second opening (32) in the disc (12) and thus the second return line (32, 36) closes, in a second position of the thermal shut-off valve (31, 32), when a predetermined temperature is exceeded, the bi-metal cantilever rod (30) against the pretensioning force of the cantilever spring (29) with its free end (34) the second closing member (31), the free end (31) of the cantilever spring (29) lifts from the second opening (32) in the disc (12) and thus opens the second return line (32, 36) . 7. viscous coupling according to claim 6, characterized geken ¬ characterized in that the cantilever spring (29) at its free end (31) has a hook-shaped bent extension (33), the free end (34) of the bimetallic cantilever (30) in a space (35) protrudes between the extension (33) and the free end (31) of the cantilever spring (29), moves freely in the intermediate space (35) and only touches the extension (33) when a predetermined temperature is exceeded in order to Open the thermal shut-off valve (12, 31). 8. viscous coupling according to claim 6, characterized in that the bimetallic cantilever (30) additionally forms the cantilever spring (29) and thus also the second closing member (31). 9. viscous coupling according to claim 6, 7 or 8, characterized in that the closing member (31) moves axially parallel. 10. viscous coupling according to claim 6, 7 or 8, characterized in that the closing member (31) moves in a plane perpendicular to the axis of rotation.