GB2185322A

GB2185322A - Pitot tube arrangement for hydraulically controlled transmissions

Info

Publication number: GB2185322A
Application number: GB08700126A
Authority: GB
Inventors: Fritz Henken
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1986-01-09
Filing date: 1987-01-06
Publication date: 1987-07-15
Also published as: FR2592690A1; GB2185322B; FR2592690B1; GB8700126D0; DE3600410C1

Abstract

The invention relates to a Pitot tube arrangement for determining the speed of rotation of a component in a hydraulically controlled transmission. The arrangement includes an annular duct (2') connected to the component (1') of which the rotational speed is to be determined. The a Pitot tube (6') projects into the duct (2') and faces the direction of rotation. The duct (2') is supplied with liquid by way of the Pitot tube (6'), liquid being conveyed to the Pitot tube (6') by way of a throttle (19) and a control valve (8) for regulating the pressure across the throttle (19). The control valve (8) in the preferred embodiment is connected to a pump and serves to regulate flow from the pump through the throttle (19) to the annular duct in such a manner as to maintain across the throttle a pressure difference determined by the Pitot pressure and the pump pressure. <IMAGE>

Description

SPECIFICATION Pitot tube arrangement for hydraulically controlled transmissions The invention relates to a Pitottubearrangementfor determining the speed of rotation of a component in a hydraulically controlled transmission, in particular for a motorvehicle, the arrangement comprising an annular duct connected to the component of which the rotational speed is to be determined, into which duct the end of a Pitottube projects and faces the direction of rotation, the annular duct being open on its inner side facing the axis of rotation and being supplied with liquid either byway of leakage from the lubricating system of the transmission or byway of its own supply lines.

Acontrol device for a converter clutch is known from DE-OS 33 06 000, in which a Pitottube arrangement is provided on the driven part, in this case being the turbine of the torque converter. As indicated inthedescription of Fig u re 4 of that specification, in the last paragraph on page 11 and the first paragraph on page 12, the open annularduct of the Pitot tu be arrang ement is su ppl ied with liquid from the lubricating system by way of a th rottling member.

This manner of supplying the Pitottube arrangement with liquid is in general use and operates without difficulty, provided that in the vicinityofthethePitottubearrangementliquidis present which can be diverted out ofthe lubricating system easilyandto an adequatedegreethrough adjacent transmission elements.

In the case of certain transmission arrangements, in particular in the case oftransmission arrangements in which a forward-gear/reverse-gear planetary shifting mechanism is arranged in the front end ofthe gearbox adjacent a belt-drive transmission and the pressure medium pump ofthe gearbox is arranged at the other end of the gearbox, driven by a central pump shaft, the Pitottube arrangement must be disposed in a region ofthe gearbox casing in which liquid from the lubrication system is not available.

Therefore, in order to supply the Pitottube arrangementwith liquid in such a case, it has had to be provided with itsownfillingtubewhichwas connected to the control valve assembly in the gearbox casing and which had to ensure an adequate supply of liquid.

The provision of such a special arrangement of an additional filling tube is relatively complicated and expensive and the invention seeks to provide a Pitot tube arrangement which, with little structural outlay, can be reliably supplied with the required liquid even in a regionofthetransmission inwhich liquidfrom the lubrication system is not readily available.

In accordance with the invention, fluid is introduced into the annular duct by way ofthe Pitot tube itself and the liquid supply is controlled in dependence upon the prevailing pump pressure and Pitot pressure.

According to a first aspect ofthe invention, there is provided a Pitottube arrangementfordetermining the speed of rotation of a component in a hydraulically controlled transmission, the arrangement including an annular duct connected to the component of which the rotational speed iso be determined, into which duct the end of a Pitottube projects and faces the direction of rotation, the annular duct being open on its inner side facing the axis of rotation and being supplied with liquid, characterised in that the open annular duct is supplied with liquid by way ofthe Pitottube, liquid being conveyed to the Pitot tube by way of a throttle and a control valve for regulating the pressure across the throttle.

According to a second aspect of the present invention, a Pitottubearrangementfordetermining the speed of rotation of a component in a hydraulically controlled transmission, the arrangement including an annularduct connected to the component of which the rotational speed isto be determined, into which duct the end of a Pitottube projects and faces the direction of rotation, the annularduct being open on its inner side facing the axis of rotation and being supplied with liquid, characterised in that the open annular duct is supplied with liquid by way ofthe Pitottube, liquid at a higher pressure level being conveyed to the Pitot tube byway of a control valve and a throttle, the control valve comprising a valve spool which is disposed within a valve bore, has three control lands and is acted upon between two of the control lands with pump pressure, at one end by a spring and the Pitot pressure and at the other end by the regulated filling pressure and the throttle being disposed between the filling pressureareaandthePitot pressure area ofthe control valve.

In thisway, on the one handthefilling tubewith the required ducts to the control valve casing can be dispensedwith, and on the other hand, byvirtueof the dimensioning of the spring force, the diameter ratio D1/D2 ofthe spool lands and the throttle size, an optimum filling time of the annular duct of the Pitot tube arrangement can be achieved and a compensation ofthe leakage losses can be ensured in any operating state.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1shows a priorartliquid supplyfora Pitot tube arrangement when disposed at an inconvenient position in the gearbox housing, and Figure2 shows a similarview of an embodiment of the invention.

In the case ofthe prior of the art construction shown in Figure 1, a central pump drive shaft 1 has connected to it an inwardly open annular duct 2 of a Pitottube arrangement 3 which needs to be provided with its own filling tube 4 because of its being situated in an inconvenient position inside the gearbox casing. Thefilling tube 4 suppliesthe annular duct 2 with liquid by way of ducts from the control valve assembly 5, so that the Pitottube 6, which likewise projects into the annular duct 2, can produce rotational speed dependent Pitot pressure and transmitthis pressure by way of ducts 7 to the control valve assembly 5 of the gearbox.

Figure 2 shows a Pitottube arrangement 3' according to the invention, which again essentially comprises a central pump drive shaft 1', an annular duct 2' open towards the inside and a Pitottube 6'.

In orderto supply the annular duct 2' with liquid a control valve 8 is provided, which comprises a valve spool 10 disposed within a stepped valve bore 9 having parts with with different diameters. The spool 10 has control lands, 11,12 and 13, of which control land 1 1/D1 has a smaller diameterthan control land 1 3/D2.

The valve spool lOis acted upon by pump pressure byway of a duct 1 4which opens into the valve bore 9 between the control lands 12 and 13. The control land 13 is acted upon bya compression spring 15/F and, byway of a duct 16, by the Pitot pressure. When the land is movedtothe left,asviewed, bythe spring 15/F, the pump pressure is applied to a duct 17 to establish a filling pressure which is separated from the Pitot pressure by a throttle 19/B and which is also applied to the other end ofthevalve spool 18 bywayofa duct 18.

Thefillingflowofliquidcan be adjusted byway of the force F of the spring 15, the diameter ratio ofthe control lands 1 lID1 to that ofcontrol land 13/D2and the size B ofthethrottle screen 19 in such a way that an optimum time forfilling the annular chamber 2 with liquid is achieved and a compensation ofthe leakage losses is ensured at any operating position.

The filling flow of liquid flowing through the throttle 19 is affected by the difference in pressure between the pump pressure and the Pitot pressure.

Since this filling quantity must first compensate the leakage ofthe Pitottube arrangement after the annularchamber2has beenfilled, an expedient regulation ofthe quantity takes place. In this connection, on account the control valve 8 a constant or proportional difference in pressure is set atthe throttle 19.

Claims

1. A Pitottube arrangementfor determining the speed of rotation of a component in a hydraulically controlled transmission, the arrangement including an annularduct connected to the component of which the rotational speed isto be determined, into which duct the end of a Pitottube projects and faces the direction of rotation,the annularductbeing open on its inner side facing the axis of rotation and being supplied with liquid, characterised in that the open annularduct is supplied with liquid bywayofthe Pitottube, liquid being conveyed to the Pitottube by way of athrottle and a control valve for regulating the pressure across the throttle.

2. An arrangementas claimed in claim l,wherein the control valve is connected to a pump and serves to regulate flow from the pump through the throttle tothe a annular duct in such a manner as to maintain across thethrottle a pressure difference determined by the Pitot pressure and the pump pressure.

3. A Pitottube arrangementfor determining the speed of rotation of a component in a hydraulically controlled transmission,the arrangement including an annular duct connected to the component of which the rotational speed isto be determined, into which duct the end of a Pitottube projects and faces the direction of rotation,the annularduct being open on its inner side facing the axis of rotation and being supplied with liquid, characterised in that the open annularduct is supplied with liquid bywayofthe Pitottube, liquid at a higher pressure level being conveyed to the Pitot tube by way of a control valve and a throttle, the control valve comprising a valve spool which is disposed within a valve bore, has three control lands and is acted upon between two of the control landswith pump pressure, atone end by a spring and the Pitot pressure and at the other end by the regulated filling pressureandthethrottle being disposed between the filling pressure area and the Pitot pressure area of the control valve.

4. An arrangement as claimed in claim 3,wherein the bore of the valve is a stepped bore and the lands at the two ends ofthevalve spool are of different diameter.

5. An arrangement construction arranged and adapted to operate substantially as herein described with reference to and as illustrated in Figure 2 ofthe accompanying drawings.