GB2180603A

GB2180603A - Change-speed gearbox lubrication

Info

Publication number: GB2180603A
Application number: GB08610127A
Authority: GB
Inventors: Harald Fitzner
Original assignee: Ford Motor Co
Current assignee: Ford Motor Co
Priority date: 1985-09-21
Filing date: 1986-04-25
Publication date: 1987-04-01
Also published as: GB8610127D0

Abstract

A change-speed gearbox for a motor vehicle, having an oil sump containing oil for lubrication and means for varying the level of the oil in the sump in dependence upon the operating conditions. The means for varying the oil level comprise a member 12 which is variably immersible in the sump oil 9 and means 14 for adjusting the extent of immersion of the member 12 in the oil 10 in the sump 9 in dependence upon the operating conditions, in particular temperature, to reduce the oil level and thus viscous drag when the oil is cold. The positioning of the member 12 is independent of the rotation of the transmission elements 3, 5 so that the level of the oil can set before the transmission elements are driven. In alternative embodiments the level is varied by an expansible element or by a scoop. <IMAGE>

Description

SPECIFICATION Change-speed gearbox The invention relates to change-speed gearbox and is applicable in particular to a gearbox of layshaft gearing design for use in a motor vehicle transmission.

A change-speed gearbox of layshaft gearing design, for motor vehicles, in which an oil sump is formed in the gearbox casing and in which the oil in the sump reaches different levels under different operating conditions, is known from the German Offenlegungsschrift (Laid-Open Specification) 31 20 394.

In the case of this change-speed gearbox, lateral reservoirs are provided into which the viscous cold oil is raised and from which it can return to the oil sump through suitable openings when it becomes less viscous with increased temperature.

This known change-speed gearbox thus has the disadvantage that the transmission elements must first start in cold viscous oil.

A step, for achieving an early reduction of the drag on the transmission elements when starting in viscous cold oil without the use of reservoirs, is already known from GB-A-2 147 064. Even in the case of this change-speed gearbox, however, the transmission elements in viscous cold oil must start with a normal level of oil.

The invention seeks to provide an improved gearbox in which it is possible for the transmission elements to start in a reduced oil level in the gearbox sump, that is to say, a gearbox in which the level of the oil in the sump can be altered before the transmission elements of the gearbox are driven.

According to a first aspect of the present invention, there is provided a change-speed gearbox for a motor vehicle, having an oil sump containing oil for lubrication and means for varying the level of the oil in the sump in dependence upon the operating conditions, the means for varying the oil level in the sump comprising a member which is variably immersible in the sump oil and means for adjusting the extent of immersion of the member in the oil in the sump in dependence upon the operating conditions.

According to a second aspect of the invention, there is provided a change-speed gearbox for a motor vehicle, having an oil sump containing oil for lubrication and means for varying the level of the oil in the sump in dependence upon the operating conditions, the means for varying the oil level in the sump comprising a displacement member immersible in the sump oil and means for varying the volume of the displacement element immersed within the oil in dependence upon the operating conditions.

The displacement member may be a solid body which is immersible to different extents in the sump oil by means of a suitable actuator.

Alternatively, the displacement member may be an expandable member which is immersed in the sump oil at least when expanded. In this case, the displacement member may be an inflatable member connected to a supply of pressure medium but more preferably is filled with a material which expands upon being heated.

According to a further aspect of the invention, there is provided a change-speed gearbox for a motor vehicle, having an oil sump containing oil for lubrication and means for varying the level of the oil in the sump in dependence upon the operating conditions, wherein the means for varying the oil level comprises a scoop member, means for lowering the scoop into the oil in the sump and raising the scoop member to withdraw oil from the sump and thereby lower oil level level, and means for enabling oil scooped out of the sump to return to the sump so as again to raise the oil level.

By virtue of the fact that in the various embodiments of the invention, the oil level in the sump of the gearbox in which the transmission elements must start with viscous cold oil, can be set in a simple manner when the gearbox is still at rest, an improvement of the shifting action is achieved in the cold state of the change-speed gearbox. Engine starting is also assisted as there is less drag caused by the transmission. These advantages are achieved, however, without detriment to the lubrication under normal running conditions, when the oil is less viscous, as the oil level can then be raised as necessary.

A further advantage resides in the fact that the level of oil splashing in the gearbox, can be controlled to reduce the resulting losses in efficiency.

For moving the displacement member or the scoop member, simple mechanical lever actuators or electromagnetic solenoid actuators are possible, while for the inflatable displacement element plastics material containers or sheetmetal containers in the shape of bellows can be employed.

In the latter case, the extension of the bellows may be achieve by the use of a source of pressure medium but it is also possible and simpler to fill the inflatable displacement element with a material which changes its volume considerably as a direct function of the prevailing temperature, so that an automatic adjustment of the oil level can be achieved.

Such materials are known for example from the field of expansion material elements for the thermostat control on cooling water circuits in motor vehicles.

The invention will now be described further, by way, of example, with reference to the accompanying drawings, in which: Figure 1 is a vertical cross-section through a gearbox showing diagrammatically a displacement member according to the invention; Figure 2 is a vertical longitudinal section through the gearbox of Fig. 1, in which the oil levels possible on account of the two different positions of the displacement member are indicated; Figure 3 is a vertical cross-section through a gearbox with a diagrammatic illustration of a possible embodiment of the displacement element, and Figure 4 is a vertical cross-section through a gearbox casing with a diagrammatic illustration of a scoop member according to the invention.

In the gearbox 1 illustrated in Fig. 1 a plurality of transmission elements disposed on a main transmission shaft 2 are shown only symbolically by a circle 3 indicated by dashdot lines, while the transmission elements mounted on a layshaft 4 are shown symbolically by a circle 5 indicated by dash-dot lines.

A selector mechanism 6 comprising selector forks 7 and 8 is provided in known manner in the upper region of the gearbox 1.

The lower part of the gearbox 1 forms an oil sump 9, which is filled with a specific quantity of oil 10 to reach the height of the level designated 11. On the right hand side of the gearbox 1 a displacement member 12 of a specific volume is shown in continuous lines in its raised position, in which it does not affect the level of the oil 10 in the sump 9.

If the displacement member is lowered by means of a suitable device into its lowered position indicated by broken lines, it displaces a corresponding volume of oil thereby raising the oil level in the sump to the level represented by a dash-dot line 13. The transmission elements 5 revolving with the layshaft 4 are thereby immersed more deeply into the oil and on account of the increased splashing increase the amount of oil acting to lubricate the upper regions of the gearbox casing.

As evident in particular from the different oil levels indicated in a corresponding manner in Fig. 2-level 11 with cold viscous oil and level 13 with heated thinner oil-a substantially reduced braking effect is exerted upon the transmission elements of the layshaft 4 during cold starting, as a result of which the known gear-shifting problems occurring in the synchromesh devices on account of the viscosity of the oil can be substantially reduced.

Suitable actuators 14 in the form of lever arrangements or in the form of electromag netic solenoid arrangements, the design of which is familiar to the person skilled in the art without more detailed explanation, are of course necessary for moving the displacement member 12.

In Fig. 3, an expandable displacement ele ment 15 is disposed in the gearbox 1' im mersed in the oil 10' within the oil sump 9', The displacement element 15 in this case is in the form of a bellows which can be inflated by means of an applied pressure medium or can be filled with a material which automatically expands when heated, By virtue of such an embodiment of displacement elements with an automatically operating material filling, mechanical actuators which in themselves are complicated and liable to breakdown can be avoided.

In Fig. 4, a hollow scoop member 16 is disposed in the gearbox 1" and is capable of being immersed into and lifted out of the oil 10" in the oil sump 9". The scoop member 16 is moved out of the sump oil 10" in dependence upon the operating conditions, being raised as a rule during the state of rest of the motor vehicle when oil is cold. When the scoop member 16 is raised with the oil cold and viscous, it lifts from the sump 9" its own volume of oil, thereby lowering the height of the oil remaining in the sump 9" to the level 11".

When the change-speed gearbox is operated the transmission elements are then started in the desired manner at a lowered oil level.

When the entire gearbox has been heated by prolonged running sufficiently for the oil to pass into its highly liquid state, the oil which is scooped up flows through openings 17 in the scoop back into the oil 10" and increases the height of the latter so that it reaches the higher oil level 13".

It is additionally pointed out that the actuator for the hollow scoop member 16 must be designed in such a way that in cold weather it is actuated for a short time before operating the change-speed gearbox, so as to raise the scoop member 16.

Claims

1. A change-speed gearbox for a motor vehicle, having an oil sump containing oil for lubrication and means for varying the level of the oil in the sump in dependence upon the operating conditions, the means for varying the oil level in the sump comprising a member which is variably immersible in the sump oil and means for adjusting the extent of immer sion of the member in the oil in the sump in dependence upon the operating conditions.

2. A change-speed gearbox for a motor vehicle, having an oil sump containing oil for lubrication and means for varying the level of the oil in the sump in dependence upon the operating conditions, the means for varying the oil level in the sump comprising a dis placement member immersible in the sump oil and means for varying the volume of the dis placement element immersed within the oil in dependence upon the operating conditions.

3. A change-speed gearbox according to Claim 2, wherein the displacement member is a solid body which is immersible to different extents in the sump oil by means of a suitable actuator.

4. A change-speed gearbox according to Claim 2, wherein the displacement member is an expandable member which is immersed in the sump oil at least when expanded.

5. A change-speed gearbox according to claim 4, wherein the displacement member is an inflatable member conneected to a supply of pressure medium.

6. A change-speed gearbox according to claim 4, wherein the expandable member is filled with a material which expands upon being heated.

7. A change-speed gearbox for a motor vehicle, having an oil sump containing oil for lubrication and means for varying the level of the oil in the sump in dependence upon the operating conditions, wherein the means for varying the oil level comprises a scoop member, means for lowering the scoop into the oil in the sump and raising the scoop member to withdraw oil from the sump and thereby lower oil level level, and means for enabling oil scooped out of the sump to return to the sump so as again to raise the oil level.

8. A change-speed gearbox according to any preceding claim, wherein the means for varying the level of the oil are operative automatically to lower the oil level in the sump when the oil is cold and viscous so as to reduce the drag on the transmission elements.

9. A change-speed gearbox for a motor vehicle, constructed arranged and adapted to operate substantially as herein described with reference to and as illutrated in the accompanying drawings.