WO2006110945A1

WO2006110945A1 - Clutch device

Info

Publication number: WO2006110945A1
Application number: PCT/AU2006/000507
Authority: WO
Inventors: Darren Lee Firth; Richard Terrence Tamba; Stephen Tapper; Simon Paul Fitzgerald
Original assignee: NT Consulting International Pty Ltd
Current assignee: NT Consulting International Pty Ltd
Priority date: 2005-04-18
Filing date: 2006-03-13
Publication date: 2006-10-26
Anticipated expiration: 2007-10-18

Abstract

A clutch device (10) for coupling rotatable first and second components (12, 14), the device (10) including a first clutch (18) capable of slippage for controlling synchronisation between the first and second components (12, 14), and a second clutch (20) adapted to be engaged when the components are at least substantially synchronised, so as to lock the first and second components (12, 14) together.

Description

CLUTCH DEVICE

Field of the Invention

This invention relates to a clutch device, and more particularly, though not exclusively, to a synchronising clutch device having a friction clutch and a dog clutch.

Background of the Invention

It is known for drive to be transmitted via a friction clutch or a dog clutch.

However, each of these types of clutches has disadvantages. A friction clutch is commonly used in an automotive transmission for transmitting drive from a driving component to a driven component in a vehicle drive train. A friction clutch has the advantage that it is able to perform clutch slippage between a driving clutch surface and a driven clutch surface so that the clutch is able to be progressively engaged to gradually equalise rotational speeds of the two components. However, owing to the ability of the friction clutch surfaces to slip one relative to the other, friction clutches have the disadvantage that a relatively large friction clutch is needed to transmit high torque, and a relatively large coupling force is required to hold the clutch surfaces in engagement so as to avoid unwanted clutch slippage during transmission of high torque.

A dog clutch is commonly used in marine transmissions, and is capable of transmitting high torque for a relatively small clutch owing to the clutch forming a locked toothed coupling when engaged which prevents slippage of the clutch once it is engaged. However, a dog clutch has the disadvantage that it is not capable of clutch slippage and, as such, is not suitable in many applications where it is necessary for there to be clutch slippage in order to provide smooth engagement between the driving component and the driven component.

Examples of the present invention seek to provide a clutch which overcomes or at least alleviates one or more of the above problems. Summary of the Invention

In accordance with one aspect, there is provided a clutch device for coupling rotatable first and second components, the device including a first clutch capable of slippage for controlling synchronisation between the first and second components, and a second clutch adapted to be engaged when the components are at least substantially synchronised, so as to lock the first and second components together.

Preferably, the second clutch is not capable of clutch slippage. More preferably, the second clutch has mating parts including a first part with one or more protruding teeth and a second part with one or more indentations for receiving the one or more protruding teeth so as to rotationally lock the two parts.

Preferably the first clutch is a friction clutch.

Preferably, the clutch device is movable between a disengaged condition in which the first and second clutches are disengaged, an engaged condition in which the first and second clutches are engaged, and an intermediate condition in which the first clutch is at least partially engaged and the second clutch is disengaged.

Preferably, the clutch device has a single piston which is movable in a single stroke so as to cause the clutch device to move from the disengaged condition to the intermediate condition to the engaged condition, in that order.

Alternatively, the clutch device has a first piston for engaging the first clutch and a second piston for engaging the second clutch. In one form, the first and second pistons are operable by a shared hydraulic line such that their operation is mutually dependent, and the pistons are configured so that the clutch device moves from the disengaged condition to the intermediate condition to the engaged condition, in that order, with increasing pressure in the shared hydraulic line. Preferably, the pistons are configured by selection of piston return springs and/or by selection of relative piston sizes and/or by selection of one or more hydraulic flow constrictors. In another form, the first and second pistons are operable independently.

In accordance with another aspect, there is provided a method of engaging first and second components into driving engagement, including the steps of: engaging a first clutch capable of slippage so as to control synchronisation of rotation between the first and second components; and engaging a second clutch when the components are at least substantially synchronised so as to lock the first and second components together.

Preferably, the first and second components are locked together in a toothed coupling.

Brief Description of the Drawings

The invention is described, by way of non-limiting example only, with reference to the accompanying drawings in which:

Figure 1 is a diagrammatic cross-sectional view of a clutch device according to a first example;

Figure 2 is a diagrammatic cross-sectional view of a clutch device according to a second example;

Figure 2a is a diagrammatic sketch of a portion of mating parts of a toothed clutch of a clutch device;

Figure 2b is a diagrammatic cross-sectional view of a variation of the clutch device shown in Figure 2; and

Figure 3 is a diagrammatic cross-sectional view of a variation of the clutch device shown in Figure 1. Detailed Description

Figure 1 shows a synchronising clutch device 10 for coupling a first component 12 to a second component 14 so that rotation is able to be transmitted from one component to the other. More particularly, in the example shown, the first component 12 is driven by an engine or the like, and the synchronising clutch device 10 is for engaging the second component 14 with the first component 12 such that the second component 14 is driven by the first component 12. Both the first component 12 and the second component 14 are rotatable about a common axis 16.

In one example, the first component 12 may be driven by an internal combustion engine mounted in a vehicle, and the second component 14 may be coupled to driving wheels of the vehicle. In another example, the first component 12 may be driven by an internal combustion engine of a marine craft, and the second component 14 may be coupled to a driving propeller of the marine craft. In other examples, the second component 14 may be the driving component of the pair, and the first component 12 may be the driven component of the pair.

The synchronising clutch device 10 includes a first clutch 18 capable of slippage, and a second clutch 20, the first clutch 18 being engageable so as to control synchronisation of rotation of the first and second components 12, 14 through clutch slippage. The second clutch 20 is adapted for engagement when the components 12, 14 are at least substantially synchronised so as to lock together the first and second components

12, 14. In the example shown in Figure 1, the first clutch 18 is a friction clutch, having a first set of friction plates 22 mounted to the first component 12 and a second set of friction plates 24 mounted to the second component 14.

The second clutch 20 is of a type known as a "dog clutch" and comprises a first part 28 having a plurality of protruding teeth 30, and a second part 32 having a plurality of indentations 34 for receiving the plurality of protruding teeth 30 so as to rotationally lock the two parts 28, 32 (and thus also the two components 12, 14). The first part 28 is integral to a piston 26 mounted on the first component 12, and the second part 32 is integral to the second component 14. . In the synchronising clutch device 10 of Figure 1, the single piston 26 is operable for engaging both clutches 18, 20. The piston 26 is mounted for axial movement within a cylinder 35 formed in the_. first component 12, and is movable parallel to the axis 16. The piston 26 is movable in response to pressure of hydraulic fluid fed to an apply chamber 38 between the piston 26 and the first component 12. A return spring in the form of a disc spring 40 (for example a "Belleville Washer") biases the piston 26 to the return position shown in Figure 1, in which both clutches 18, 20 are disengaged. In the example shown, two disc springs 40, 40a are used. It will be understood by those skilled in the art that in alternative examples, the return spring may take other forms such as, for example, a helical spring.

The apply chamber 38 is sealed by way of O-rings 39 which prevent escape of hydraulic fluid between the cylinder 35 and the piston 26. With both clutches 18, 20 disengaged, the second component 14 is free to rotate relative to the first component 12, and thus the synchronising clutch device 10 is in a disengaged condition. In an example where the synchronising clutch device 10 is used in a drive train of a vehicle, the disengaged condition may be used where the vehicle is stationary with its engine running (eg. at idle).

The synchronising clutch device 10 is movable between the disengaged condition in which the first clutch 18 and the second clutch 20 are disengaged, an engaged condition in which the first clutch 18 and the second clutch 20 are engaged, and an intermediate condition (being intermediate the disengaged condition and the engaged condition) in which the first clutch 18 is at least partially engaged and the second clutch 20 is disengaged. In the example shown in Figure 1, the single piston 26 is movable in a single stroke (ie. from its return position to its apply position) so as to cause the synchronising clutch device 10 to move from the disengaged condition to the intermediate condition to the engaged condition, in that order. Accordingly, from the disengaged condition where the second component 14 is free to rotate relative to the first component 12, the piston 26 is applied to bring the clutch device 10 to the intermediate condition in which synchronisation of rotation of the two components 12, 14 is controlled through clutch slippage. Once at least substantially synchronised, the piston 26 is then applied further to bring the clutch device 10 to the engaged condition in which the second clutch 20 is engaged, thus locking together the first and second components 12, 14.

To ensure effective synchronisation of rotation of the first and second components 12, 14 prior to engagement of the second clutch 20, the positions of the piston 26 corresponding to the intermediate condition and the engaged condition are tuned by selection of shape, size and configuration of the piston 2ό relative to the clutches 18, 20, and by selection of the size and rate of the disc springs 40, 40a. Synchronisation of rotation of the first and second components 12, 14 may involve acceleration of one of the components 12, 14 and/or deceleration of the other component 14, 12. Activation of the engaged condition may be triggered by sensing of a speed differential between the first and second components 12, 14 reaching a predetermined value which facilitates engagement of the second clutch 20 to lock together the first and second components 12, 14.

An alternative example of a synchronising clutch device is shown in Figure 2. Like features are indicated with like reference numerals. The main difference between the synchronising clutch device 10 of Figure 1 and the synchronising clutch device 10 of Figure 2 is that the latter has two pistons 26a, 26b for separate activation of the first and second clutches 18, 20. More particularly, the synchronising clutch device 10 of Figure 2 has a first piston 26a for engaging the first clutch 18 and a second piston 26b for engaging the second clutch 20.

In Figure 2, the second component 14 is in two parts 14a, 14b which are rigidly fixed one to the other so as to rotate together about the axis of rotation 16. The first component 12 is located between the two parts 14a, 14b.

In one form, the first and second pistons 26a, 26b are operable by a shared hydraulic line such that their operation is mutually dependent, and the pistons 26a, 26b are configured so that the synchronising clutch device 10 moves from the disengaged condition to the intermediate condition to the engaged condition, in that order, with increasing pressure in the shared hydraulic line. Such configuration (or "tuning") may be performed by selection of piston return springs 41a, 41b and/or by selection of relative sizes of the pistons 26a, 26b, and/or by use of one or more hydraulic flow constrictors to reduce pressure of fluid entering the apply chambers 38a, 38b of the pistons 26a, 26b via the respective feed lines 42a, 42b.

In another form, the first and second pistons 26a, 26b are operable independently, for example by each of the feed lines 42a, 42b being fed by different valves of a hydraulic control system.

A piston dam 44 is provided so as to avoid self-apply of the first piston 26a due to centrifugal force on fluid in the apply chamber 38a when the first component 12 is rotating about the axis 16, at least for normal operating conditions.

With reference to Figure 2a which shows a top view of the second clutch 20 of the synchronising clutch device 10 of Figure 2, the protruding teeth 30 may be tapered for facilitating engagement of the second clutch 20, particularly in circumstances where the protruding teeth 30 do not line up with the receiving indentations 34, such that minor relative rotation between the first and second components 12, 14 is required for locking to occur. Software may also be used to facilitate alignment for engagement of the second clutch, for example by controlling the clutch device to retry engagement if necessary.

Figure 2b shows a variation of the clutch device 10 of Figure 2. Like features are labelled with like reference numerals. The difference resides in that the clutch device 10 shown in Figure 2b has been modified so that the spring retainer 45 is sealed to provide a piston dam 44a. This enables hydraulic pressure to be applied to both sides of the second piston 26b. Accordingly, the clutch device 10 is able to be hydraulically disengaged so that there is no need for either or both return springs 41 a, 41b.

^■ Another variation is shown in Figure 3, which shows a clutch device 10 similar to the clutch device of Figure 1. Like features are labelled with like reference numerals. The clutch device 10 has been modified to include a second piston 26b seated within a cylinder formed in the first piston 26. Accordingly, the second piston 26b is able to be extended from the first piston 26 by applying hydraulic pressure to an apply chamber located between the pistons 26, 26b. Accordingly, the second piston 26b is able to engage the second clutch 20 independently of operation of the first clutch 18. The pistons 26, 26b may be activated by either a single circuit or separate circuits. Operation by separate circuits enables separate forces for different tasks.

Advantageously, the clutch devices described above incorporate a toothed clutch which enables transmission of high torques for a relatively small clutch unit, and a relative small friction clutch which has sufficient capacity for reducing a speed difference of the first and second components so as to enable smooth or relatively smooth engagement of the toothed clutch.

The above clutch devices have been described by way of example only and modifications are possible within the scope of the invention. For example, the synchronising clutch device shown in Figure 2 may also be provided with a disc spring (not shown) between the first piston 26a and the first clutch 18 to assist in control of application of the first clutch 18, and to cushion application of the first clutch 18. It will also be understood by those skilled in the art that application of the clutches 18, 20 may be controlled by way of electro-hydraulic, air over hydraulic, air only, electromagnetic, and/or hydraulic apparatus. The first clutch 18 may also be represented by a cone clutch or single plate clutch or similar.

The design of the synchronising clutch device 10 may also include a position indicating device and an electronic control combined with software by which the position can be electronically controlled and the rate of apply can be electronically controlled. The clutch device 10 may be calibrated using hydraulic flows, spring loads, feed/bleed orifices, pressure, magnetic force, clutch pack clearances, friction surface types, oil types, friction groove patterns, etc.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A clutch device for coupling rotatable first and second components, the device including a first clutch capable of slippage for controlling synchronisation between the first and second components, and a second clutch adapted to be engaged when the components are at least substantially synchronised, so as to lock the first and second components together.

2. A clutch device as claimed in claim 1, wherein the second clutch is not capable of clutch slippage.

3. A clutch device as claimed in claim 2, wherein the second clutch has mating parts including a first part with one or more protruding teeth and a second part with one or more indentations for receiving the one or more protruding teeth so as to rotationally lock the two parts.

4. A clutch device as claimed in any one of claims 1 to 3, wherein the first clutch is a friction clutch.

5. A clutch device as claimed in any one of claims 1 to 4, wherein the clutch device is movable between a disengaged condition in which the first and second clutches are disengaged, an engaged condition in which the first and second clutches are engaged, and an intermediate condition in which the first clutch is at least partially engaged and the second clutch is disengaged.

6. A clutch device as claimed in claim 5, wherein the clutch device has a single piston which is movable in a single stroke so as to cause the clutch device to move from the disengaged condition to the intermediate condition to the engaged condition, in that order.

7. A clutch device as claimed in claim 5, wherein the clutch device has a first piston for engaging the first clutch and a second piston for engaging the second clutch.

8. A clutch device as claimed in claim 7, wherein the first and second pistons are operable by a shared hydraulic line such that their operation is mutually dependent, and the pistons are configured so that the clutch device moves from the disengaged condition to the intermediate condition to the engaged condition, in that order, with increasing pressure in the shared hydraulic line.

9, A clutch device as claimed in claim 8, wherein the pistons are configured by selection of piston return springs.

10. A clutch device as claimed in claim 8 or claim 9, wherein the pistons are configured by selection of relative piston sizes.

11. A clutch device as claimed in any one of claims 8 to 10, wherein the pistons are configured by selection of one or more hydraulic flow constrictors.

12. A clutch device as claimed in claim 7, wherein the first and second pistons are operable independently.

13. A method of engaging first and second components into driving engagement, including the steps of: engaging a first clutch capable of slippage so as to control synchronisation of rotation between the first and second components; and engaging a second clutch when the components are at least substantially synchronised so as to lock the first and second components together.

14. A method of engaging first and second components into driving engagement as claimed in claim 13, wherein the first and second components are locked together in a toothed coupling.