GB2147064A

GB2147064A - Change-speed gearbox

Info

Publication number: GB2147064A
Application number: GB08421363A
Authority: GB
Inventors: Gustav Sabel
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1983-09-23
Filing date: 1984-08-22
Publication date: 1985-05-01
Also published as: GB2147064B; DE3334411C1; FR2552517A1; FR2552517B1; GB8421363D0

Abstract

The invention relates to a reduction change-speed gearbox for a motor vehicle having a sump which is fitted with a partition (15) lying close to the gear rings on the layshaft (4) in order to prevent viscous drag on the gear rings when the lubricant is cold and thereby improve gear changes when the vehicle is started from cold. <IMAGE>

Description

SPECIFICATION Change-speed gearbox The invention relates to a change-speed gearbox for motor a vehicle.

In a motor change-speed gearbox in reduction gearing form, freely rotatable gearwheels are mounted on an input shaft and on an output shaft coaxial with the input shaft and mesh constantly with corresponding gear rings on a lay-shaft disposed parallel parallel to the input and output shafts. When drive is to be transmitted through the meshing gears, the freely rotatable gearwheels are locked to their respective shafts.

In order to achieve such coupling smoothly, synchromesh arrangements connect the freely rotatable gearwheels with further gear rings fast in rotation with the input and output shafts. Synchromesh clutches are mounted on the input and output shafts which, upon axial displacement of a gearshift sleeve by means of a selector fork, act to press synchronising rings against bevels of the freely rotatable gearwheels. After synchronization has been attained, the gear-shift sleeve is slit through into clutch toothing on the freely rotatable gearwheels in order to achieve a driving connection to the output shaft.

With this known arrangement in changespeed gearboxes, it has been found that during the sliding of the gearshift sleeve through the toothing of the synchronizing ring, a slight jolt is experienced. The cause of this jolt is believed to be viscous drag on the gearwheels in the short interval between the release of the frictional driving force on the freely rotatable gearwheel and the engagement of the toothing of the gearshift sleeve in the clutch toothing of the freely rotating gearwheel.

This braking is understandably considerable during cold weather when the viscosity of the lubricant is higher and this leads, when starting a motor vehicle, to undesirable grating while engaging the gears, which largely disappears, however, as soon as the gear oil has reached its normal running temperature.

The present invention seeks to suppress such grating in a cold change-speed gearbox of a motor vehicle and at the same time to improve the efficiency of the change-speed gearbox, which is low in this operating range.

According to the present invention, there is provided a change-speed gearbox for a motor vehicle having an oil sump and a partition disposed in the sump, wherein the partition is of arcuate section when viewed along the axis of the gearbox and is contoured to fit closely about the different gears on the lay-shaft, the upper edge of the partition being arranged above the level of the oil in the sump and serving during rotation of the gears to separate any excess of oil adhering to the surface of the different gears prior to the surface reentering the oil in the sump and the lower edge of the partition being arranged beneath the oil level, the partition extending in close proximity to each of the gears on the lay-shaft over an arc corresponding to a substantial portion of the part of each gear immersed in the oil in the sump.

In accordance with a second aspect of the invention, there is provided a change-speed reduction gearbox for a motor vehicle having a sump formed within the casing of the gearbox and divided by a partition, the partition forming a collecting space which is divided off from the main volume of the sump, is open at the top and communicates below with the main volume of the sump by way of an opening, characterised in that in its course parallel to the gearbox axis the partition is matched to the different diameters of the gear rings and the intervening portions of the layshafts, in that on one side of the gears the edge of the partition rises contrary to the direction of rotation of the layshaft above the oil level in the sump and is arranged close to the gear rings and on the other side extends at an increasing distance from the gear rings, terminating below the oil level.

By virtue of the construction of the partition in the sump of the gearbox, the lubricant oil picked up in the form of a viscous thick coating particularly during cold weather is separated by the upper edge of the partition wall lying close to the gear rings and builds up in the collecting space on the side of the partition remoter from the gears. No oil can reach the gear rings over an area of preferably 180 of a revolution on account of the partition wall, as a result of which the undesired braking effect is avoided.

The oil remaining within the teeth of the gear rings is quite sufficient for the necessary lubrication in this operating range.

When the entire change-speed gearbox and the lubricant oil have been heated up to their operating temperature after some distance has been covered, the now fluid lubricant oil in the sump is once more quite capable of penetrating the gap between the gear rings and the partition to ensure proper lubrication of the gear rings of the layshaft.

It is noted that partitions have previously been incorporated in sumps. In German Offenlegungsschrift a partition wall is provided to avoid unnecessarily high splashing of the crown wheel rotating in an excessively high oil sump during travel of the motor vehicle, as this leads to undesired heating of the gear lubricant oil. The action sought can only be attained, however, if the lubricant oil is sufficiently fluid, is flung upwards and reaches the collecting space open at the top. At low temperatures, at which gear lubricant oil behaves with a similar viscosity to cold honey or syrup, the partition wall does not make any difference to the differential gearing.

German Offenlegungsscrhrift 25 53 010 discloses a gearbox for motor vehicles in which an oil sump is partitioned by a plate to prevent swells from occurring in the oil sump.

This is to ensure that a suction pipe of a lubricant pump will always remain immersed in the lubricant oil and so cannot accidently suck in air.

The above publications are concerned therefore with reducing swirling under normal running temperatures and and do not suggest a solution to the problem of noisy gear changing when the engine is cold.

The partition wall is preferably in the form of a pressed metal sheet which is secured and supported in the gearbox case by upper holding brackets and lower supporting brackets.

However, as an alternative, the partition may be formed as a one-piece plastics moulded part with suitable brackets.

As a further alternative, the partition wall may form part of the caing of the gearbox.

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a vertical section through a change-speed gearbox in reduction gearing form, in particular for motor vehicles, and Figure 2 is a vertical section along the line Il-Il in Fig. 1.

The change-speed gearbox in reduction gearing form illustrated in Fig. 1 is a 5-speed gearbox known per se with one-rod shifting, and hereinafter only those parts which are necessary for understanding the invention will therefore be provided with reference numerals and explained.

An input shaft 2 and an output shaft 3 disposed coaxially thereto are rotatably mounted in the upper region of a gearbox case 1. A layshaft 4 is rotatably mounted in the lower region of the gearbox case parallel to the input and output shafts 2 and 3 respectively, a so-called layshaft gear cluster being arranged rotatably mounted on a stationary axis in generally known manner.

A plurality of freely rotating gearwheels, which cooperate with corresponding synchromesh clutches, are disposed on the output shaft 3. Gear rings in mesh engagement with the freely rotating gearwheels are provided on the layshaft 4. Of these freely rotating gearwheels, the synchromesh clutches and the gear rings, reference is made only to one of these arrangements for explanatory purposes.

A synchromesh clutch 5 for the 3rd and 4th gears essentially comprises a synchronizing hub 6, a gearshift sleeve 7 and corresponding synchronizing locks 8. A freely rotating gearwheel 9 for the 3rd gear is in constant mesh engagement with a corresponding gear ring 10 on the layshaft 4. A synchronizing cone 11 with a following clutch toothing 1 2 is formed on the freely rotating gearwheel 9. A synchronizing ring 13, which comprises a synchronizing toothing 14, is disposed on the synchronizing cone 11.

In order to engage the 3rd gear, the gearshift sleeve 7 is moved towards the synchron izing ring 13, and then the synchronizing locks 8 push the synchronizing ring 1 3 against the synchronizing cone 11 and thereby cause a retardation or acceleration of the freely rotating gearwheel 9 to the speed of the gearshift sleeve 7.

As soon as synchronization has been achieved, the gearshift sleeve 7 can be engaged, and it then strikes the known chamfering angle of the synchronizing toothing 14, so that the synchronizing ring 1 3 is released in order to permit a further movement of the gearshift sleeve 7 into the clutch toothing 1 2 on the freely rotating gearwheel 9.During this brief period of time between the breaking away of the synchronizing ring 1 3 and the engagement of the toothing of the gearshift sleeve 7 in the clutch toothing 1 2 of the freely rotating gearwheel the synchronization already achieved at the beginning ceases on account of the fact that the gear ring 10 in question, which like all the other gear rings has previously been retarded by the viscous lubricant oil, transmits this retardation to the freely rotating gearwheel 9 in mesh engagement with it.

The lubricant oil coating adhering to the gear rings of the layshaft is separated therefrom after the first revolution of the said layshaft 4 by a partition wall 1 5 which is specially arranged in the gearbox case 1 and the position of which may be seen in particular in Fig. 1.

The partition wall 1 5 is disposed in the gearbox case 1 is arranged in such a way that-with respect to a normal oil level 1 6 and a direction of rotation of the layshaft 4 corresponding to the arrow A-on its side facing contrary to the direction of rotation it is raised up by about 45 above the oil level 1 6 and is situated at a short distance of about 1 mm from the corresponding gear ring in each case, whereas on the other side it extends at an increasing distance until about 5mm from the gear rings and terminates about 45 below the oil level 16. In this connection, in its course parallel to the gearbox axis, the partition wall 15 is made to match the different diameters of the gear rings on the layshaft and thickness of the intervening portions of the shaft, as best illustrated by Fig. 1.

In the shown in the Figure the partition 1 5 is in the form of a pressed metal sheet and is secured and supported in the gearbox case 1 in a suitable manner by way of upper holding brackets 1 7 and lower supporting brackets.

Where appropriate, there may be further provided above the raised side of the partition wall 1 5 an upper baffle plate 1 9 which also permits a separation of viscous lumps of lubricant oil from the toothings of the freely rotat ing gearwheels.

A partition with the different holding and supporting brackets may alternatively be formed at a one-piece plastics moulded part of suitable material.

It is also possible in a complete rearrangement of a gearbox casing, to construct a partition as an integral component of the gearbox casing.

Claims

1. A change-speed gearbox for a motor vehicle having an oil sump and a partition disposed in the sump, wherein the partition is of arcuate section when viewed along the axis of the gearbox and is contoured to fit closely about the different gears on the lay-shaft, the upper edge of the partition being arranged above the level of the oil in the sump and serving during rotation of the gears to separate any excess of oil adhering to the surface of the different gears prior to the surface reentering the oil in the sump and the lower edge of the partition being arranged beneath the oil level, the partition extending in close proximity to each of the gears on the lay-shaft over an arc corresponding to a substantial porportion of the part of each gear immersed in the oil in the sump.

2. A change-speed reduction gearbox for a motor vehicle having a sump formed within the casing of the gearbox and divided by a partition, the partition forming a collecting space which is divided off from the main volume of the sump, is open at the top and communicates below with the main volume of the sump by way of an opening, characterised in that in its course parallel to the gearbox axis the partition is matched to the different diameters of the gear rings and the intervening portions of the layshaft, in that on one side of the gears the edge of the partition rises contrary to the direction of rotation of the layshaft above the oil level in the sump and is arranged close to the gear rings and on the other side extends at an increasing distance from the gear rings, terminating below the oil level.

3. A change-speed gearbox as claimed in claim 1 or 2, wherein the partition is in the form of a pressed metal sheet which is secured and supported in the gearbox case by supporting brackets.

4. A change-speed gearbox as claimed in claim 1 or 2, wherein the partition wall is formed of a one-piece plastics moulded part with suitable holding and supporting brackets.

5. A change-speed gearbox as claimed in claim 1 or 2, wherein partition wall is formed as an integral part of the gearbox casing.

6. A change-speed gearbox for a motor vehicle, constructed substantially as herein described with reference to and as illustrated in the accompanying drawings.