GB2620709A

GB2620709A - A gearbox

Info

Publication number: GB2620709A
Application number: GB2316349.6A
Authority: GB
Inventors: Redmond Dennis
Original assignee: Smart Manufacturing Technology Ltd
Current assignee: Smart Manufacturing Technology Ltd
Priority date: 2020-02-19
Filing date: 2020-02-19
Publication date: 2024-01-17
Anticipated expiration: 2040-02-19
Also published as: GB2620709B; GB202316349D0

Abstract

A gearbox 10 comprising at least one pair of meshed gears 12 and a lubricant supply system 16, wherein the lubricant supply system comprises at least one outlet 20 that supplies lubricant to the at least one pair of meshed gears. The lubricant supply system comprises a deflector 52 to inhibit the rebound of lubricant away from the pair of meshed gears located at the mesh point of the gears. The lubricant supply system further comprises a controller 24 that varies the flow of lubricant through the or each outlet depending on a state of transmission of said pair of meshed gears. The volume of lubricant supplied to the pair of meshed gears may depend on the load through the gears i.e. whether that particular gear ratio is selected or not.

Description

A gearbox

FIELD OF THE INVENTION

The present invention relates to a gearbox comprising a lubricant supply system, and to a method of supplying lubricant to meshed gears.

BACKGROUND OF THE INVENTION

It is known to lubricate gears housed within a gearbox by arranging a shaft or shafts carrying gears in a lubricant sump, so that the gears will churn through the lubricant. In order for all of the gears to be lubricated in all conditions, however, a large amount of lubricant must be held within the sump. The lubricant within the sump is constantly being churned, resulting in power loss and increased lubricant temperatures.

It is known to address these problems with the use of injection lubrication systems, where lubricant is filtered and pumped to the gears. In some known systems, a spray bar is used to direct jets of lubricant directly into each pair of meshed gears at the point of mesh of that pair. However, lubricant is continuously pumped through the system, resulting in continuous churning of the lubricant within the system, and increased lubricant temperatures.

An unloaded pair of meshed gears does not require the same amount of lubricant as a loaded pair of meshed gears, i.e. the pair of meshed gears through which driving force is transmitted. Directing an equal amount of lubricant to every pair of meshed gears in a gearbox, regardless of whether or not each pair of meshed gears is transmitting load, results in more lubricant being moved around the system than is necessary.

In addition, in an injection lubrication system, where jets of lubricant are directed into the mesh of each pair of meshed gears, lubricant rebounds from the mesh due to the rotation of the gears. That is, not all of the lubricant that is directed towards the point of mesh between the gears reaches that point of mesh. More lubricant than is required by the gears must therefore be used in order to ensure that the gears receive enough lubricant. In addition, where lubricant is directed towards the point of mesh of the gears in a direction other than vertically downwards, some lubricant is redirected due to gravity, and will not reach the point of mesh between the gears. This leads to more lubricant circulating the system than is required by the gears.

The present invention seeks to overcome or at least mitigate the problems of the prior art.

SUMMARY OF THE INVENTION

According to an embodiment there is provided a gearbox comprising at least one pair of meshed gears and a lubricant supply system, wherein the lubricant supply system comprises at least one outlet configured to supply lubricant to said pair of meshed gears; and a pump configured to move lubricant through the system. The lubricant supply system further comprises a controller configured to vary the flow of lubricant through the or each outlet depending on a state of transmission of said pair of meshed gears.

Regulation of the flow of lubricant to a pair of meshed gears depending on the state of transmission of that pair of meshed gears provides more efficient distribution of lubricant. The amount of lubricant moving through the system can be reduced, so that churning of the lubricant is reduced. A reduction in churning leads to a corresponding reduction in power loss due to churning, and a reduction in the unwanted increase of oil temperatures due to churning.

In exemplary embodiments, each pair of meshed gears has a first, loaded, state of transmission, where a driving force is transmitted between a first gear and a second gear; and a second, unloaded, state of transmission, where no driving force is transmitted between the first and second gears, and wherein the controller is configured to reduce the flow of lubricant through the or each outlet when said pair of meshed gears is in the second state.

Reducing the flow of lubricant to a pair of meshed gears where less lubricant is required, i.e. to an unloaded pair of meshed gears, allows a reduction of the amount of lubricant moving through the system. The lubrication supply system has improved efficiency without a reduction in the amount of lubricant directed towards a loaded pair of meshed gears, as the maximum possible flow of lubricant is not delivered through all outlets at all times.

In exemplary embodiments, the lubricant supply system comprises at least one flow control valve, and the controller is configured to operate said flow control valve depending on a state of transmission of said pair of meshed gears.

In exemplary embodiments, the lubricant supply system comprises a flow control valve associated with the or each outlet, and the controller is configured to operate the or each flow control valve depending on a state of transmission of a pair of meshed gears associated with said associated outlet.

The flow control valve(s) allow the controller to regulate lubricant flow to each outlet, so that the amount of lubricant directed to each pair of meshed gears can be varied according to the state of transmission of that pair of meshed gears.

In exemplary embodiments, the or each flow control valve is movable between a first, fully open, position configured to allow lubricant to flow through the associated outlet at a maximum rate, and a second, partially open, position configured to allow lubricant to flow through the associated outlet at a reduced rate.

The controller can simply and effectively regulate flow from each outlet by moving the associated flow control valve between first and second positions. As the flow control valves are moved between fully and partially open positions, there is no closed position, and lubricant is always supplied to each pair of meshed gears.

In exemplary embodiments, the or each flow control valve comprises a solenoid, and the controller is configured to activate said solenoid to vary flow through said outlet.

Solenoids provide a simple and effective means of varying flow rate. The controller is able to quickly adjust flow of lubricant through each outlet.

In exemplary embodiments, the controller is configured to activate said solenoid to reduce flow through said outlet.

Activation of the solenoid leading to a reduction in flow through the outlet means that maximum flow is, advantageously, the normal state of the valve, and provides a fail-safe for the system -if there is disruption of power to the controller, or if communication between the controller and the solenoid is disrupted, the valve will move to the open position, and maximum flow will be provided to the pair of meshed gears in question.

In exemplary embodiments, the or each flow control valve comprises a flow regulator configured to control the flow of lubricant through the outlet upon activation of said solenoid.

In exemplary embodiments, the flow regulator comprises magnetic material configured to provide actuation of the flow regulator upon activation of the solenoid.

Flow can thereby be regulated quickly and simply, upon activation of the solenoid by the controller.

In exemplary embodiments, the or each control valve comprises a resilient biasing mechanism configured to resiliently bias said flow control valve towards an open position.

Resiliently biasing the control valves towards an open position provides a fail-safe for the system. The gears should not operate without lubrication, even when unloaded, as damage to the gears could be caused, for example through overheating. If the controller fails, the resilient biasing means will cause each valve to return to an open position, and lubricant will flow at a maximum rate through each outlet.

In exemplary embodiments, the resilient biasing mechanism comprises a compression spring.

A compression spring is a simple, reliable and effective means of resiliently biasing the control valve towards an open position.

In exemplary embodiments, the controller is configured to vary the flow of lubricant through the or each outlet to between 10% and 100% of flow depending on a state of transmission of said pair of meshed gears.

In exemplary embodiments, each pair of meshed gears has a first, loaded, state of transmission, where a driving force is transmitted between a first gear and a second gear; and a second, unloaded, state of transmission, where no driving force is transmitted between the first and second gears; and wherein the controller is configured to reduce the flow of lubricant through the or each outlet to between 10% and 75% of maximum flow when said pair of meshed gears is in the second state.

In exemplary embodiments, the controller is configured to reduce the flow of lubricant through the or each outlet to between 20% and 40% of maximum flow when said pair of meshed gears is in the second state.

Such a reduction in flow to an unloaded pair of meshed gears reduces the amount of lubricant moving around the system with the advantages set out above, whilst supplying enough lubricant to the unloaded pair of meshed gears to avoid damage and maintain the gears at a suitable temperature.

In exemplary embodiments, the gearbox further comprises a sensor configured to detect which, if any, of said pair or pairs of meshed gears is in a state of transmission where driving force is transmitted between the gears of that pair, and to provide an indication to the controller of which of said pair or pairs of meshed gears is in said state of transmission.

The sensor allows the controller to detect a pair of meshed gears which requires 100% of maximum lubricant flow, and so to detect the pair or pairs of meshed gears which can safely operate under reduced lubricant flow, i.e. those pairs of meshed gears which are unloaded.

In exemplary embodiments, the gearbox comprises a gearshift mechanism, and the sensor is a position sensor configured to detect the position of the gearshift in order to provide an indication to the controller of which, if any, of said pair or pairs of meshed gears is in said state of transmission.

The position of the gearshift mechanism being used to give an indication of the pair of meshed gears transmitting a driving force is an efficient and reliable means of indicating to the controller which, if any, pair of meshed gears is loaded. The controller can then reduce the flow of lubricant to the remaining gears.

In exemplary embodiments, the gearbox is an automated manual transmission gearbox comprising a transmission control unit, and the sensor is configured to determine from the transmission control unit which, if any, of said pair or pairs of meshed gears is in said state of transmission.

In an automated manual transmission, the transmission control unit can be used to provide an indication of which pair of meshed gears is loaded to the controller.

In exemplary embodiments, the sensor is configured to detect from the transmission control unit, advance indication of a change of gear and indication of the pair of meshed gears to be loaded, and the controller is configured to increase the flow of lubricant to said pair of meshed gears to be loaded in advance of said change of gear.

As the transmission control unit is able to anticipate changes of gear, this information can be used by the controller to increase flow of lubricant to a particular pair of meshed gears shortly before the gear change occurs, ensuring that the necessary flow of lubricant is in place prior to the pair of meshed gears being loaded.

In exemplary embodiments, the lubricant supply system further comprises a lubricant temperature sensor configured to provide an indication to the controller of the lubricant temperature.

In exemplary embodiments, the controller is configured to operate the lubricant supply system such that there is maximum flow of lubricant through every one of the outlets until the lubricant temperature is above a predetermined threshold. Providing maximum flow of lubricant through the lubricant supply system serves to warm up the lubricant. Although it is desirable to maintain lubricant at lower temperatures than the lubricant can reach in an unregulated lubricant supply system, as set out above, it is also desirable to warm the lubricant on start-up of the system such that the desired lubricant viscosity is reached. The temperature sensor allows the control system to determine the point at which the optimum lubricant temperature is reached, and only then to regulate flow of lubricant to unloaded pairs of meshed gears. The lubricant will thereby reach the optimum temperature more quickly than when the flow of lubricant to the or each outlet is regulated.

In exemplary embodiments, the or each outlet comprises a deflector configured to inhibit rebound of lubricant away from a pair of meshed gears.

The deflector blocks lubricant that is splashed away from a pair of meshed gears and redirects that lubricant back towards the mesh of the pair of meshed gears.

In particular, where lubricant is injected towards a pair of meshed gears in a direction other than vertically downwardly, e.g. horizontally, a significant proportion of lubricant does not reach the area of engagement between the gears. The deflector acts to contain the lubricant as it is injected towards the gears, and to direct it towards the area of engagement. Efficiency of the system is thereby increased, as a greater proportion of lubricant reaches its target.

In exemplary embodiments, the or each deflector comprises a pair of arms configured to extend either side of said pair of meshed gears.

Such an arrangement efficiently redirects rebounded lubricant back towards the pair of meshed gears.

In exemplary embodiments, the or each deflector is arranged in relation to a corresponding pair of meshed gears such that said pair of arms is configured to extend either side of said pair of meshed gears at a point of mesh of said pair of meshed gears.

In exemplary embodiments, the or each deflector comprises a body defining a first plane, and said first plane extends substantially parallel to a longitudinal axis of each of said pair of meshed gears.

In exemplary embodiments, the or each deflector comprises opposing arms extending from said body substantially perpendicular to said first plane.

The shape of the deflector allows the arms to extend around the point of engagement of the gears, and so to deflect a significant amount of rebounded lubricant.

In exemplary embodiments, the lubricant supply system comprises a lubricant sump.

There is also provided a method of supplying lubricant via a lubricant supply system to a pair or pairs of meshed gears, the lubricant supply system having at least one outlet configured to supply lubricant to a pair of meshed gears, and a pump configured to move lubricant through the system; the method comprising the steps of: a) determining the state of transmission of said pair or pairs of meshed gears; and b) varying the flow of lubricant through said outlet according to the state of transmission of said pair of meshed gears.

Variation of the flow of lubricant to a pair of meshed gears depending on the state of transmission of that pair of meshed gears provides more efficient distribution of lubricant. The amount of lubricant moving through the system can be reduced, so that churning of the lubricant is reduced. A reduction in churning leads to a corresponding reduction in power loss due to churning, and a reduction in the unwanted increase of oil temperatures due to churning.

In exemplary embodiments, said pair of meshed gears has a first, loaded, state of transmission, where a driving force is transmitted between a first gear and a second gear; and a second, unloaded, state of transmission, where no driving force is transmitted between the first and second gears and wherein, in step c), the flow of lubricant through the outlet is reduced when, in step b), it is determined that said pair of meshed gears is in the second, unloaded, state.

In exemplary embodiments, in step c), the flow of lubricant is reduced to between 20 10% and 75% of maximum flow.

In exemplary embodiments, the flow of lubricant is reduced to between 20% and 40% of maximum flow.

In exemplary embodiments, the lubricant supply system comprises a temperature sensor, the method further comprising the step of: c) determining whether lubricant within the lubricant supply system is above a predetermined temperature; and, in step b), reducing the flow of lubricant through said outlet only when said lubricant is above said predetermined temperature.

Providing maximum flow of lubricant through the lubricant supply system serves to warm up the lubricant. Although it is desirable to maintain lubricant at lower temperatures than the lubricant can reach in an unregulated lubricant supply system, as set out above, it is also desirable to warm the lubricant on start-up of the system such that the desired lubricant viscosity is reached. The temperature sensor allows the control system to determine the point at which the optimum lubricant temperature is reached, and only then to regulate flow of lubricant to unloaded pairs of meshed gears. The lubricant will thereby reach the optimum temperature more quickly than when the flow of lubricant to the or each outlet is regulated.

In exemplary embodiments, the lubricant supply system comprises a sensor configured to detect the state of transmission of said pairs of meshed gears, and the method further comprises, in step a), determining which of said pairs of meshed gears is in a state of transmission where driving force is transmitted between the gears of that pair; and further comprises the step of: d) providing an indication of which of said pairs of meshed gears is in said state of transmission.

In exemplary embodiments, said sensor is a position sensor configured to detect the position of a gearshift.

The position of the gearshift mechanism being used to give an indication of the pair of meshed gears transmitting a driving force is an efficient and reliable means of indicating to the controller which pair of meshed gears is loaded. The controller can then reduce the flow of lubricant to the remaining gears.

In exemplary embodiments, said gearbox is an automated manual transmission gearbox comprising a transmission control unit, and in step e), the sensor is configured to detect the state of transmission of said pairs of meshed gears from the transmission control unit.

In exemplary embodiments, the method further comprises, in step a) detecting advance indication of a change of gear and indication of the pair of meshed gears to be loaded from the transmission control unit; and further comprises the step of: e) increasing the flow of lubricant to said pair of meshed gears in advance of said change of gear.

There is further provided a lubricant supply system for a gearbox, wherein the lubricant supply system comprises a lubricant sump; at least one outlet configured to supply lubricant to a pair of meshed gears; and a pump configured to move lubricant through the system. The lubricant supply system further comprises a controller configured to vary the flow of lubricant through the or each outlet depending on a state of transmission of said pair of meshed gears.

In exemplary embodiments, the lubricant supply system comprises a flow control valve, and the controller is configured to operate the flow control valve depending on a state of transmission of said pair of meshed gears.

In exemplary embodiments, the lubricant supply system comprises a flow control valve associated with the or each outlet, and the controller is configured to operate the or each flow control valve depending on a state of transmission of said pair of meshed gears.

In exemplary embodiments, the controller is configured to vary the flow of lubricant through the or each outlet to between 10% and 100% of maximum flow depending on a state of transmission of said pair of meshed gears.

In exemplary embodiments, each pair of meshed gears has a first, loaded, state, where a driving force is transmitted between a first gear and a second gear; and a second, unloaded, state, where no driving force is transmitted between the first and second gears; and wherein the controller is configured to reduce the flow of lubricant through the or each outlet to between 100/0 and 75% of maximum flow when said pair of meshed gears is in the second state.

In exemplary embodiments, the system further comprises a sensor configured to detect which of said pairs of meshed gears is in a state of transmission where driving force is transmitted between the gears of that pair, and to provide an indication to the controller of which of said pairs of meshed gears is in said state of transmission.

The sensor allows the controller to detect a pair of meshed gears which requires 1000/o of maximum lubricant flow, and so to detect the pair or pairs of meshed gears which can safely operate under reduced lubricant flow, i.e. those pairs of meshed gears which are unloaded.

In exemplary embodiments, the system is for a gearbox comprising a gearshift mechanism, and the sensor is a position sensor configured to detect the position of the gearshift in order to provide an indication to the controller of which of said pairs of meshed gears is in said state of transmission.

In exemplary embodiments, the system is for an automated manual transmission gearbox comprising a transmission control unit, and the sensor is configured to determine from the transmission control unit which of said pairs of meshed gears is in said state of transmission.

In exemplary embodiments, the controller is configured to operate the lubricant supply system such that there is maximum flow of lubricant through each and every one of the outlets until the lubricant temperature is above a predetermined threshold.

In exemplary embodiments, the or each outlet comprises a deflector configured to inhibit rebound of lubricant away from a corresponding pair of meshed gears.

The deflector blocks lubricant that is splashed away from a pair of meshed gears and redirects that lubricant back towards the pair of meshed gears mesh. In particular, where lubricant is injected towards a pair of meshed gears in a direction other than vertically downwardly, e.g. horizontally, a significant proportion of lubricant does not reach the area of engagement between the gears. The deflector acts to contain the lubricant as it is injected towards the gears, and to direct it towards the area of engagement. Efficiency of the system is thereby increased, as a greater proportion of lubricant reaches its target.

In exemplary embodiments, the or each deflector is arranged in relation to the pair of meshed gears such that said pair of arms is configured to extend either side of said pair of meshed gears at a point of mesh of said pair of meshed gears. In exemplary embodiments, the or each deflector comprises a body defining a first plane, and said first plane extends substantially parallel to a longitudinal axis of each of said pair of meshed gears.

There is also provided a gearbox comprising at least one pair of meshed gears, an injection lubricant supply system comprising an outlet configured to supply lubricant to said pair of said gears, and a deflector configured to inhibit rebound of lubricant away from said pair of meshed gears.

In exemplary embodiments, the or each deflector is arranged at one of said outlets.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is an isometric view of a gearbox with a lubricant supply system according to an embodiment; Figure 2 is a side view of the gearbox of Figure 1; Figure 3 is a schematic diagram of the gearbox of Figures 1 and 2; Figure 5 a, 4b and 4c are cross-sectional views through a flow control valve of the lubricant supply system of Figures 1 to 3, showing the flow control valve in different states; Figure 5 is a view of a flow control system of the lubricant supply system; Figure 6 is a cross-sectional view of the gearbox of Figure 2 along line A:A; Figure 7 is a detail view B of the gearbox of Figure 6; Figure 8 is an isometric view of a lubricant deflector for the lubricant supply system of Figure 1; Figure 9a is an isometric view of a lubricant deflector according to a further embodiment with a pair of meshed gears; and Figure 9b is a further isometric view of the lubricant deflector of Figure 9a.

DETAILED DESCRIPTION OF EMBODIMENT(S)

A gearbox is shown in Figures 1 and 2, indicated generally at 10. The gearbox housing is not shown, to improve clarity. The gearbox 10 has a series of pairs of meshed gears 12. Each pair of meshed gears has a first gear 12a and a second gear 12b. The first gears 12a are mounted on a first shaft 14, and the second gears are mounted on a second shaft (not shown). The gearbox 10 of this embodiment is of a type for use in a heavy vehicle such as a truck. However, the embodiment described below is suitable for use with other types of vehicle and/or machine, and for other gearbox arrangements.

The gearbox 10 has a lubricant supply system 16. The lubricant supply system 16 is an injection type lubricant supply system and is configured to deliver lubricant to each pair of meshed gears 12.

Figure 3 shows a schematic of the gearbox 10 including the lubricant supply system 16. The lubricant supply system 16 has a lubricant sump 18 in which lubricant for the system is held.

The lubricant supply system 16 has a series of outlets 20 through which lubricant is supplied to the pairs of meshed gears 12. As shown in Figures 1, 2 and 3, each outlet 20 is associated with a pair of meshed gears 12 to which the outlet 20 is arranged to provide lubricant.

The lubricant supply system 16 has a pump 22 for moving lubricant around the lubricant supply system 16. Lubricant is pumped from the sump 18 and through the outlets 20 to the pairs of meshed gears 12, then drains to the sump 18 under gravity.

The lubricant supply system 16 has a controller 24. The controller 24 varies the flow of lubricant through the outlets 20. The amount of lubricant directed to each pair of meshed gears 12 depends on the state of transmission of that pair of meshed gears 12.

The sump 18 has a first, coarse, lubricant filter 19 configured to filter lubricant before lubricant reaches the pump 22. A second, finer, lubricant filter 21 is located within the system 16 between the pump 22 and the outlets 20.

Each pair of meshed gears 12 has a first, loaded, state of transmission, and a second, unloaded, state of transmission. When in the first, loaded, state, a driving force is transmitted between the first gear 12a and the second gear 12b of that pair of meshed gears 12. That is, torque is transmitted between the gears 12a, 12b of a pair of meshed gears 12.

In the second, unloaded, state, no such driving force is transmitted between the first 12a and second 12b gears. The unloaded gears 12a, 12b continue to rotate with the shafts 14 on which they are supported. As the gears 12a, 12b continue to rotate, lubricant must be provided to the unloaded pairs of meshed gears 12 to prevent damage being caused to the gears 12a, 12b, and to prevent overheating. However, a pair of meshed gears 12 in an unloaded state does not require the same amount of lubricant as a pair of meshed gears 12 in a loaded state, due to the decreased amount of torque being transmitted, and a reduced requirement for cooling. It has advantageously been recognised that the amount of lubricant supplied to an unloaded pair of meshed gears 12 can be reduced, and so the efficiency of the lubrication system can be improved.

The controller 24 is configured to reduce the flow of lubricant through the outlets 20 when the pairs of meshed gears 12 with which the outlets 20 are associated are in an unloaded state. The controller 24 acts to ensure that the unloaded pairs of meshed gears 12 continue to receive a suitable amount of lubricant through the outlets 20.

In this embodiment, each outlet 20 is associated with a flow control valve 26, by which the flow of lubricant through that outlet 20 is varied. The controller 24 operates the flow control valves 26 to control the flow of lubricant through the outlets 20 depending on the state of transmission of the associated pair of meshed gears 12.

Figures 4a, 4b and 4c each provide a cross-sectional view of a flow control valve 26. Figure 4a shows the flow control valve 26 in a first, fully open, position. When the flow valve 26 is in this first fully open position, lubricant can flow through the outlet 20 at a maximum rate, i.e. at substantially 100% of the maximum flow rate.

The controller 24 is configured to operate the flow valve 26 to be in this fully open position, as shown in Figure 4a, when the pair of meshed gears 12 with which the flow control valve 26 is associated is in the first, loaded, state.

Figure 4b shows the flow control valve 26 in a second, partially open, position. In this position, the flow control valve 26 allows lubricant to flow through the associated outlet 20 at a reduced rate, as discussed in further detail below.

The flow control valve 26 does not have a fully closed position. That is, there is no position of the flow control valve 26 where flow of lubricant through the outlet 20 is prevented. No pair of meshed gears 12 is without a supply of lubricant whilst the gearbox 10 is operating.

As shown in Figures 4a and 4b, each flow control valve 26 has a solenoid 28 by which the flow control valve 26 is activated. In this embodiment, the solenoid 28 is activated by the controller 24 when the flow of lubricant through each outlet 20 is to be varied. That is, in this embodiment, activation of the solenoid 28 by the controller 24 results in a reduction of lubricant flow through the outlet 20. Figure 4a shows the flow control valve 26 when the solenoid 28 is not activated, and the flow control valve 26 is in the first, fully open position. Figure 4b shows the flow control valve 26 when the solenoid 28 is activated by the controller 24, and the flow control valve 26 is, as a result, in the second, partially open, position.

As non-activation of the solenoid 28 results in the flow control valve 26 being in the first, fully open position, a fail-safe mechanism is provided. Figure 4c shows the flow control valve 26 where communication between the controller 24 and the solenoid 28 has been disrupted. As shown in Figure 4c, any disruption of communication between the controller 24 and the solenoid 28 will result in the flow control valve 26 remaining in or returning to the fully open position, so that full flow of lubricant from the outlet 20 to the associated pair of meshed gears 12 takes place. The system thereby ensures that no pair of meshed gears 12 has a reduced amount of lubricant flow directed thereto when that pair of meshed gears 12 is in the first, loaded, state of transmission.

In the event of disruption of communication between the controller 24 and one of the solenoids 28, an indication is provided to an operator of the machine in which the gearbox 10 is installed. For example, an indicator light is provided in a cab of the machine, and is configured to alert the machine operator in the event of such disruption. In alternative embodiments, a warning sound is used to indicate such disruption.

When the gearbox 10 is at rest, each solenoid 28 is not activated, and each flow control valve 26 is in the fully open position, as shown in Figure 4a.

The solenoid 28 of each flow control valve 26 is connected to the controller 24 in this embodiment by wiring 30. Figure 5 shows an embodiment of a connection arrangement 31. The connection arrangement 31 of this embodiment has a moulded body 35 with an embedded printed circuit (not shown), and a series of connector pins 33 for connection with the solenoids 28. A connector 37 is provided for connection with the controller 24. In this embodiment, a multi-pin connector 37 is provided. In alternative embodiments (not shown), a suitable alternative connection arrangement 31 is provided.

With reference to Figures 4a and 4b, the flow control valve 26 of this embodiment has a valve member 32. The valve member 32 reduces the flow of lubricant through the outlet 20 when the flow control valve 26 is in the second, partially open, position. That is, the valve member 32 controls the flow of lubricant through the outlet 20 upon activation of the solenoid 28.

The valve member 32 is positioned within the flow control valve 26 so as to extend into the outlet 20 upon activation of the solenoid 28, and so to reduce the cross-sectional surface area of the outlet 20 in order to reduce lubricant flow rate.

When the flow control valve 26 is in the first, fully open, position, and the solenoid 28 is not activated, the valve member 32 does not extend into the outlet 20, and a maximum lubricant flow rate can occur.

The valve member 32 has a plunger 34 fixed thereto. The plunger 34 is of magnetic material, i.e. ferromagnetic material. Upon activation of the solenoid 28, the plunger 34 is attracted to the solenoid. Movement of the plunger 34 towards the solenoid 28 due to this magnetic attraction moves the valve member 32 towards the second, partially open, position where the valve member 32 extends into the outlet 20, and so reduces lubricant flow rate.

The solenoid 28, valve member 32 and plunger 34 arrangement provides a simple, responsive and effective means of flow-rate adjustment.

As shown in Figures 4a, 4b and 4c, each flow control valve 26 has a resilient biasing mechanism 36. The resilient biasing mechanism is, in this embodiment, a compression spring 36. The spring 36 is arranged to resiliently bias the flow control valve 26 towards the open position shown in Figure 4a. This arrangement provides a fail-safe for the lubrication system 16, as previously discussed.

In this embodiment, the spring 36 is arranged with the valve member 32 such that the valve member 32 extends through the spring 36, i.e. the spring 36 encircles the valve member 32. The valve member 32 has a first end 32a configured to extend into the outlet 20 in order to regulate flow as previously discussed, and a second end 32b distal the first end 32a. In this embodiment, the second end 32b has a substantially perpendicular flange 38. The flow control valve 26 has an abutment 40 configured to abut the spring 36, such that the spring 36 is constrained between the flange 38 and the abutment 40.

As shown in Figure 4b, when the solenoid 28 is activated and the valve member 32 is moved so that the flow control valve 26, is in the second, partially open, position, the spring 36 is compressed. The magnetic force of the solenoid 28 on the plunger 34 is sufficient to overcome the force exerted by the spring 36. When the solenoid 28 is deactivated by the controller 24, the spring 36 acts to return the valve member 32 to the open position, as shown in Figure 4a. In the event of disruption between the controller 24 and the solenoid 28, the spring 36 will return the valve member 32 to the open position, as shown in Figure 4c.

In this embodiment, the controller 24 is arranged to vary the flow of lubricant through each outlet 20 to 25% of the maximum flow through the outlet 20 for an unloaded pair of meshed gears 12. In alternative embodiments, the controller is arranged to reduce the flow of lubricant through an outlet to a rate of between 2 0 % and 4 0 % of maximum flow when the associated pair of meshed gears is in an unloaded state. In alternative embodiments, the controller is arranged to reduce the flow of lubricant through an outlet to between 10% and 75% of maximum flow when the associated pair of meshed gears is in an unloaded state.

Providing 25% of the maximum flow to a pair of meshed gears 12 in the second, unloaded, state is sufficient to avoid damage to the unloaded gears, and to maintain the gears 12a, 12b at a suitable temperature.

Referring now to Figure 3, the gearbox 10 has a sensor 41 for detecting which, if any, of the pairs of meshed gears 12 is in the loaded state. In this embodiment, where the gearbox 10 is arranged for manual transmission, the sensor 41 is a position sensor arranged to detect the position of a gear shift 42.

In an alternative embodiment where the gearbox is that of an automated manual transmission, the sensor is part of a transmission control unit, and determines from the transmission control unit which, if any, of the pairs of meshed gears is transmitting load. In such an automated manual transmission, the transmission control unit anticipates gear changes. The sensor detects such anticipated gear changes, and so the controller of the lubricant supply system of such an embodiment is able to anticipate increased requirements for lubricant at the pair of meshed gears to be loaded in advance of a change of gear.

The lubricant supply system 16 of this embodiment includes a lubricant temperature sensor 44. In this embodiment, the temperature sensor 44 is positioned between the sump 18 and the pump 22. In alternative embodiments, the temperature sensor is located at some other suitable location within the lubricant supply system.

In this embodiment, on start-up of the gearbox 10, the controller 24 operates the lubricant supply system 16 such that maximum flow of lubricant is sent through every outlet 20, regardless of the state of transmission of each associated pair of meshed gears 12. This maximum circulation of lubricant through the system 16 allows the lubricant to warm up, and so to reach a desired viscosity. Once the lubricant has reached a pre-determined optimum temperature or temperature range, as detected by the temperature sensor 44, the controller 24 starts to operate the lubricant supply system 16 to reduce the supply of lubricant through outlets 20 related to pairs of meshed gears 12 which are in the second, unloaded, state. In the event of lubricant temperature dropping below the pre-determined optimum range, the controller 24 returns the flow control valves 26 at every outlet 20 to the open position, so that full circulation of lubricant within the system 16 takes place until the temperature sensor 44 provides an indication that the lubricant temperature is once again within the optimum range.

The lubricant supply system 16 has a pressure sensor 46 and a pressure regulating valve 48.

Referring now to Figures 6 and 7, in this embodiment, the outlet 20 comprises a nozzle 50, shown in detail in Figure 7. The nozzle 50 directs lubricant towards a region of engagement of the first and second gears 12a, 12b of a pair of meshed gears 12. This direction of lubricant improves efficiency of the system, as it increases the proportion of lubricant that reaches the target of the region of engagement of the gears 12a, 12b.

The gearbox 10 of this embodiment has at each outlet 20 a deflector 52 configured to inhibit the rebound of lubricant away from each pair of meshed gears 12. That is, the deflectors 52 reduce the interference of turning of the gears with the supply of lubricant to the gear pair mesh.

As shown in Figures 1 and 7, in this embodiment, the deflector 52 is connected to the nozzle 50 at the outlet 20.

The deflector 52 of this embodiment is shown in further detail in Figure 8. The deflector 52 is substantially U-shaped in cross section, with a body 54 and opposing arms 56 at either side of the body 54. Each deflector 52 is arranged in association with a pair of meshed gears 12 so as to be adjacent to a region of engagement or mesh between the two gears, 12a, 12b. The arms 56 direct lubricant from the outlet towards the region of engagement between the gears 12a, 12b. Together with the body 54 of the deflector 52, the arms 56 rebound lubricant that is deflected by rotation of the gears 12a, 12b back towards the gears 12a, 12b.

The arms 56 of this embodiment are shaped to correspond to the pairs of meshed gears 12 with which the deflector 52 is associated. That is, the arms 56 are shaped such that the gears 12a, 12b can turn without hindrance from the deflector 52. The body 54 is shaped to correspond to the pairs of meshed gears 12, having a planar section 53 with curved portions 55 at either end that follow the shape of the gears 12a, 12b. The deflector 52 being shaped to follow the shape of the gears 12a, 12b improves the deflection of lubricant back towards the gear mesh.

A deflector 52 according to an alternative embodiment is shown in Figures 9a and 9b. In this embodiment, the deflector 52 has a planar body 54, and is substantially U-shaped in cross-section. Figure 9a shows the relationship between the deflector 52 and the associated pair of meshed gears 12. The body 54 defines a plane X. The deflector 52 is 5 positioned such that the plane X is substantially parallel to a longitudinal axis Y of each of the gears 12a, 12b.

The deflectors 52 of the embodiment shown in Figure 8 have the same relationship with the associated pairs of meshed gears 12, as shown in Figure 1.

Claims

Claims 1. A gearbox comprising: at least one pair of meshed gears; a lubricant supply system comprising at least one outlet configured to supply lubricant to said pair of meshed gears; and a deflector configured to inhibit rebound of lubricant away from said pair of meshed gears.
2. The gearbox of claim 1, wherein the deflector is arranged at said outlet.
3. The gearbox of claim 1 or claim 2, wherein the deflector is connected to the outlet.
4. The gearbox of claim 3, wherein the outlet comprises a nozzle, and wherein the deflector is connected to the nozzle.
5. The gearbox of any preceding claim, wherein the deflector comprises a pair of arms configured to extend either side of said pair of meshed gears.
6. The gearbox of claim 5, wherein the deflector is arranged in relation to the pair of meshed gears such that the arms are configured to extend either side of said pair of meshed gears at a point of mesh of said pair of meshed gears.
7. The gearbox of any preceding claim, wherein the deflector comprises a body defining a first plane, and said first plane extends substantially parallel to a longitudinal axis of each of said pair of meshed gears.
8. The gearbox of claim 7, wherein the deflector comprises opposing arms extending from said body substantially perpendicular to said first plane.
9. The gearbox of claim 7 or claim 8, wherein the deflector body comprises a planar portion with a curved portion at at least one end of said planar portion.
10. The gearbox of claim 9, wherein the deflector body comprises a curved portion at both ends of said planar portion.
11. The gearbox of claim 9 or claim 10, wherein said curved portion is configured to follow the shape of said gears.