GB2341436A

GB2341436A - A hydraulic pressure operated lock-up mechanism

Info

Publication number: GB2341436A
Application number: GB9919042A
Authority: GB
Inventors: Leslie John Clark
Original assignee: Individual
Current assignee: Individual
Priority date: 1998-08-15
Filing date: 1999-08-13
Publication date: 2000-03-15
Also published as: GB9817789D0; GB9919042D0

Abstract

A hydraulic pressure operated lock-up mechanism comprises a first element 1 which can be selectively locked in engagement with a second element 7. The first element 1 is journalled with a running clearance on the second element 7. Either the first or second element has a thin wall section 3. The application of a hydraulic pressure to the thin wall section 3 causes a radial deflection removing the running clearance and thereby locating the first element 1 with respect to the second element 2. A multi speed gearbox is also described (claim 14 and figs 2-4) which embodies the invention and utilises selectively operable plungers 13 to control pressurisation of the fluid.

Description

2341436 TITLE: Hydraulic pressure operated lock-up mechanism DESCREMON The

present invention relates to an hydraulic pressure operated lock-up mechanism and in particular to a means by which a first element can be selectively locked in engagement with a second element, especially rotational engagement, or released from engagement therewith.

One application of the present invention is in relation to the design of a gearbox which utilises the ability to selectively locate one element in rotational engagement with another.

An aim of the present invention is to provide a lock-up mechanism which may be used in gearbox to avoid the need for dog clutches, synchro, rings or selector forks, and which, can operate without the need for a clutch.

Accordingly, one aspect -of the present invention provides an hydraulic pressure operated lock-up mechanism comprising:- a shaft, a first element which'is directly or indirectly journalled with rLuming clearance on the shaft, and wherein one of the shaft and first element has a thin wall section forming an outer peripheral portion of the shaft or an inner bore of the first element as the case rnay be, and 2 configured for the application of hydraulic pressure thereto, means to selectively pressurise hydraulic fluid to cause the thin wall section to deflect radially within its elastic limit to cause the running clearance to be taken up and thereby locate the first element with respect to the shaft.

In a preferred embodiment the thin wall section forms part of the shaft. More particularly, the shaft comprises a main body and the thin wall section is formed by a sleeve sealingly secured to and surrounding part of the shaft body to define an annular gap between the tbin wall section of the sleeve and the part of the shaft body which it surround. The thin wall section of the sleeve may be secured to body of the sleeve by any convenient means and most conveniently by a seam welding. In an alternative construction the thin wall section is formed by machining and the shaft is reinforced internally byinsertion of one or more core elements. The shaft or the core incorporates a passageway by which hydraulic fluid is fed to the annular gap. The annula gap may have no volume when the fluid is not pressurised or it may constitute an annula chamber which always accomodates fluid.

Conveniently fluid is fed from a separate hydraulic chamber within the shaft which fluid is pressurised by movement of a piston or plunger. acting on the hydraulic fluid.

In an alternative embodiment the thin wall section comprises a sleeve defining the internal bore of said first element and pressurisation causes the sleeve to be urged radially inwardly to grip the shaft on which it is journalled. One skilled in the art wW appreciate how the teaching in relation to provision of the wall section as part of the shaft can be applied in the alternative to be part of the associated first element, which may be a gear 3 wheel or pulley etc.

In the application to a multi-speed gear box the shaft conveniently forms a layshaft of the gearbox having two or more separate thin wall sections each of which has an associated annular chamber accommodating hydraulic fluid, and means to selectively pressurise hydraulic fluid in the respective chambers. Preferably separate means is provided for controlling the pressurisation of each chamber.

Another aspect of the invention provides a gear box comprising a gear housing, an input shaft journalled in the housing, a layshaft journalled in the housing, an output shaft journalled in the housing and two or more pairs of meshed gears to transmit drive between the input shaft and the output shaft, at least one gear of each pair of gears being selectively connectable to its associated shaft by providing it with a thin wall section which is configured to be subject to hydraulic fluid under pressure and wherein said selectively connectable gears are journalled directly or indirectly with running clearance on that cir cumferential portion defined by the thin wall section, and means to selectively pressurise the hydraulic fluid to cause the thin wall section to deflect radially within its elastic limit to cause the running clearance to be taken up and thereby selectively locate said gear with respect of said shaft in order to effect a change in the gear ratio between the input and output of the gear box.

The gear box may comprise four or five pairs of gears. In one embodiment the layshaft carries four gears each of which is selectively connectable thereto.

In a preferred embodiment, an external shuttle valve or the like, controls the 4 applications of hydraulic pressure to the plunger and thereby controls operation of the lockup mechanism. However, alternative control mechanisms can be employed, including electronic solenoids and the like.

The present invention will now be described further hereinafter, by way of example only, with reference to the accompanying drawings: in which: Figure 1 is a part sectional view of a simplistic embodiment of hydraulic lock-up mechanism embodying the principals of the present invention, Figure 2 is a cross-sectional view of five speed gearbox embodying the principals of the present invention.

Figure 3 is a half-sectional view of the lay shaft according to the embodiment illustrated in figure 2 and drawn to a larger scale, and Figure 4 is a view on section line AA.

Referring firstly to figure 1, a first element, for example a gear element, is represented by component 1. It has an internal bore 3 which is received totatably as a clearance fit on a thin wall section 5 of a second element 7. The second element is representative of a shaft. It comprises a central body 9 to which the thin wall section is secured m a sealing manner by any convenient means. An annular chamber 11 is formed between the thin wall section 5 and the main body. The chamber receives hydraulic fluid. A plunger 13 controls pressurisation of the fluid within the chamber 11 by moNement in a bore 15 connected to the chamber by bore 17. The plunger is sealed with respect to. the bore in which it is axially movable.

Prior to pressurisation of the hydraulic fluid the first element is free to rotate on the thin wall sleeve. Thrust bearings 19 may be provided between the opposite axial sides of the element 1 and thrust shoulders 21 of the shaft. On pressuration, the thin wall section expands taking up the previous clearance and thereby locating the first and second elements with respect to one another. This would, for example, enable the two components to rotate as one.

To facilitate repeated operation, flexing of the thin wall section has to be within the elastic limit of the material. Examples of how the thin wall section can be constructed are given below. Preferably, the shaft and sleeve material are the same. In one embodiment the sleeve is premachined with small pockets which will form the annular chambers and the bore of the sleeve is polished, honed or baEhed to improve the surface finish and size of the bore. The sleeve is then seam-welded to the core shaft in a manner which ensures perfect weld integrity. The core has the internal features rough-machined, the cross bores drilled through and the whole finished ground to size prior to welding of the outer sleeve. Once the outer sleeve has been welded on the final machining to the internal features may be carried out. After final heat treatment the complete assembly is finfish ground to the fmal overall diameter.

There is now described with refbrence to figures 2, 3 and 4, one embodiment a fivespeed gear box incorporating an hydraulic lock-up mechanism operating on the aforedescribed principle. The gear box comprises a housing 100 having an input shaft 102 and an output shaft 104 disposed on a common axis and journalled together using a needle roller 6 105. A lay shaft 107 is journalled in the housing. The input shaft has two gears 109, 111 fixedly connected thereto by a splined connection. The output shaft has gears 113, 115 fixedly connected thereto again by way of splined connection. Each of the gears 109, 111, 113, 115 mates with a complimentary gear 117, 119, 121, 123 carried on the lay shaft 107. The internal bore of the gear wheels 117, 119, 121, 123 are journalled on the layshaft by way of respective pairs of bearings 125, 127, 129, 13 1. An internal bore of the respective gear wheels is dimensioned to be a close running clearance on the layshaft in the region of a thin wall portion thereof. The layshaft has four thin wall portions shown at 133, 135, 137 and 139, and illustrated. nmnmatically in figure 3. Each thin wall section defines part of an annular chamber formed between it and a core of layshaft and referenced 133a, 135a, 137a. and 139a respectively. Each of the annular chambers connects with a larger fluid chamber 133b, 135b, 137b and 139b connected to the annular chamber by a respective bore 133c, 135c, 137c and 239c. The respective chambers are filled with hydraulic fluid. Pressurisation of the hydraulic fluid is controlled by plungers described further hereinafter. In the case of chambers 135b and 137b the plunger is shown at 135d and 137d respectively and is disposed on the centre line of the layshaft axis. Plunger 135d passes through seals 141, 143 located in respective bores 145, 147 in part of the core of the lay shaft. Similarly plunger 137d passes through seals 151, 153 disposed in bores 155, 157. In the illustrated embodiment chambers 133b and 139b utilise three plungers 133d and 139d set on a common pitch circle diameter and sealed with respect to a core of the layshaft by seals 161, 163.

A thrust bearing 165 acts on the end of displacement rod 135d and is operated on by 7 a piston 167 which is axially moveable in a cylinder 169 which is subject to hydraulic pressure under the operation of a shuttle valve (not illustrated). Similarly displacement rod 137d is operated by movement of a piston 171 acting through thrust bearing 172. The piston is slidable in the cylinder 173 which is subject to hyc pressure under the control of a shuttle valve (not illustrated).

Each of the displacement plungers 133d is engaged by a thrust bearing 175 and these are acted on by a yoke 177 which in turn is acted on by three pistons 179 (only one is illustrated m the illustration). Hydraulic pressure is supplied to the pistons from a shuttle valve not Illustrated). Similarly the three displacement rods 139 are acted on by pistons 181 acting through yoke 183 and thrust bearings 185. Pressurisation of the hydraulic fluid in any of the chambers 133a., 135a, 137a, 139a by displacement of the appropriate displacement rods generates a gripping force between the diin wall section and the internal bore of the respective gear wheels. Only a short movement of the plungers is required to generate sufficient pressure to lock-up the gear wheel onto the lay shaft.Roller thrust bearings are preferred. The hydraulic feeds to the thrust piston is via a remote hydraulic pump and a simple two-way shuttle valve at each end. These can be electrically, pneumatically or mechanically operated.

Gear selection is achieved by switching hydraulic pressure between two sides of two shuttle valves into appropriate cylinders which act on the pistons which m turri act on the respective plungers. For example first gear ratio may be effected by locking gears 117 and 123 to the layshaft, a second gear may be established by locking gears 117 and 121 to the 8 layshaft, a third gear may be established by locking gears 119 and 123 to the layshaft, and a fourth gear may be established by locking gears 119 and 121 to the layshaft. The appropriate valves are moved to control operation of the appropriate plungers to achieve locking engagement of the gear wheel onto the layshaft. Switching to anotheT gear allows another gear to be locked to the shaft while simultaneously deflating the connection with is no longer required for the next gear ratio. It is anticipated that displacements in the order of 10mm of the displacement rods will be sufficient to generate the desired locking pressures within the annular chambers of between 450 and 800 bar with thin wall sections of the order of 0.5mm to 0.75mm.

Fifth gear can be achieved by locking together two halves of the main shaft, where a direct fifth gear is required. This could be achieved with a corresponding hydraulic operated locking device to that described above should an overdriven fifth gear be required, then the ratios can be revised appropriately and fourth mode direct. It will be appreciated that the technique could be used for securely and permanently mounting many types of assembly onto shafts ie wherever selectable drive and non-drive couplings are required.

In an alternative it is proposed to insert a split cylinder friction material between the thin wall section and the internal bore of each gear with a view to lowering operating pressures and increasing the potential power transmission. In an alternative layout the layshaft has a central bearing between gears 119, 121 and similarly the main shaft has central bearing between gears 111, 113. A dog clutch between the input and output shafts 102, 104 provides for direct drive between the input and output shafts.

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Claims

1. An hydraulic pressure operated lock-up mechanism comprising:- shaft, first element which is directly or indirectly journalled with running clearance on the shaf't, and wherein one of the shaft and first element has a thin wall section forming an outer peripheral portion of the shaft or an inner bore of the first element as the case may be, and configured for the application of hydraulic pressure thereto, means to selectively pressurise hydraulic fluid to cause the thin wall section to deflect radially within its elastic limit to cause the running clearance to be taken up and thereby locate the first element with respect to the shaft.

2. An hydraulic pressure operated lock-up mechanism as claimed in claim 1 in which the thin wall section forms part of the shaft.

3. An hydraulic pressure operated lock-up mechanism as claimed in. claim 2 in which the shaft comprises a main body and thethin wall section is f6rmed by a sleeve sealingly secured to and surrounding part of the shaft body to define an annular gap between the thin wall section of the sleeve and the part of the shaft body which it surrounds.

4. An hydraulic pressure operated lock-up mechanism as claimed in claim 2 OT 3 in which the thin wall section of the sleeve is secured to the body of the sleeve by a seam welding.

5. An hydraulic pressure operated lock-up mechanism as claimed in claim 2 or 3 in which the thin wall section is formed by machining and the shaft is reinforced internally by the insertion of one or more core elements.

6. An hydraulic pressure operated lock-up mechanism as claimed in any one of claims 3, 4 or 5 in which the shaft or the core incorporates a passageway by which hydraulic fluid is fed to the annular gap.

7, An hydraulic pressure operated lock-up mechanism as claimed in anyone of claims 3 to 6 in which the annular gap has no volume when the fluid is not pressurised.

8. An hydraulic pressure operated lock-up mechanism as claimed in any one of claims 3 to 6 in which the annular gap constitutes an annular chamber which always accomodates fluid--

9. An hydraulic pressure operated lock-up mechanism as claimed in anyone of the preceding claims in which fluid is fed from a separate hydraulic chamber within the shaft which fluid is pressurised by movement of a plunger acting on the hydraulic fluid.

10. An hydraulic pressure operated lock-up mechanism as claimed m claim 1 in which the thin wall section comprises a sleeve defining the internal bore of said first element and pressurisation causes the sleeve to be urged radially inwardly to grip the shaft on which it is journalled.

11. An hydraulic pressure operated lock-up mechanism as claimed in anyone of the preceding claims in which the first element is a gear wheel or pulley.

12. An hydraulic pressure operated lock-up mechanism as claimed in any one of the preceding claims when applied to a multi-speed gear box in which the shaft forms a lay of the gearbox having two or more separate thin wall sections each of which has an associated 0 annular chamber accommodating hydraulic fluid, and means to selectively pressurise hydraulic fluid in the respective chambers.

13. An -hydraulic pressure operated lock-up mechanism as claimed in claim 12 in which means is provided for controlling the pressurisation. of each chamber.

14. A gear box comprising a gear housing, an input shaft joumalled in the housing, a layshaft joumalled in the housing, an output shaft journalled in the housing and two or more pairs of meshed gears to transmit drive between the input shaft and the output shaft, at least one gear of each pair of gears being selectively connectable to its associated shaft by providing it with a thin wall section which is configured to be subject to hydraulic fluid under -pressure and wherein said selectively connectable gears are joumaUed directly or indirectly with running clearance on that circumferential portion defined by the thin wall section, and means to selectively pressurise the hydraulic fluid to cause the thin wall section to deflect radially within its elastic limit to cause the running clearance to be taken up and thereby selectively locate said gear with respect of said shaft in order to effect a change in the gear ratio between the input and output of the gear box.

15. A gear box as claimed in claim 14 in which the gear box comprises four or Eve pairs of gears.

16. A gear box as claimed in claim 14 in which the layshaft carries four gears each of which is selectively connectable thereto.

17. A gear box as claimed in any one of claims 14, 15 or 16 in which the hydraulic fluid is pressurized by movement of a plunger which acts thereon.

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18. A gear box as claimed in claim 17 in -which the plunger is actuated by hydraulic pressure under the control of a shuttle valve.

19. A gear box as claimed in claim 17 in which the plunger is actuated directly by an electronic solenoicL

20. A gear box as claimed m any one of claims 17 to 19 in which each gear has its own plunger.

21. An hydraulic pressure operated lock-up mechanism constructed and arranged substantially as hereinbefore described with reference to and as illustrated in.the accompanying drawing of Figure 1.

22. A gear box constructed and arranged substantially as, hereinbefore described with reference'to and as illustrated in the accompany drawings of Figure 2, 3 and 4.