GB1600244A

GB1600244A - Hydraulic control devices

Info

Publication number: GB1600244A
Application number: GB30400/77A
Authority: GB
Original assignee: Massey Ferguson Services NV
Current assignee: Massey Ferguson Services NV
Priority date: 1977-07-20
Filing date: 1977-07-20
Publication date: 1981-10-14
Also published as: DE2831784C2; IT7825735A0; FR2397969B1; BR7804720A; DE2831784A1; IT1193878B; FR2397969A1

Description

(54) IMPROVEMENTS IN HYDRAULIC CONTROL DEVICES (71) We, MASSEY-FERGUSON SER- VICES N.V., of Abraham de Veerstraat 7A, Curacao, Netherlands Antilles, a Company organised under the laws of the Netherlands Antilles, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to a hydraulic circuit for a steering mechanism having steering clutches, particularly for use in a vehicle having steerable tracks.

Steering of such a vehicle is achieved by operation of a clutch provided in the drive to each of a pair of tracks wherein disengagement of one of such clutches results in disconnection of the drive to one of the tracks whilst the drive is maintained to the other track. This latter track thus causes the vehicle to slew round to achieving a change of direction.

Steering clutches are conveniently either engaged or disengaged hydraulically, by passing, for example, high pressure oil into a piston and cylinder arrangement by opening a control valve. When the valve is closed, oil may drain from the oil line supplying the clutch, thus producing an operation lag when the valve is opened whilst the high pressure oil refils the oil line and the cylinder.

The present invention seeks to provide means by which the above operation lag is avoided.

According to the present invention we provide a hydraulic circuit for a steering mechanism of a tracked vehicle having a pair of tracks driven by a prime mover via hydraulic steering clutches, said circuit including a pair of steering control valves, hydraulic lines connecting each steering valve with a respective one of said steering clutches, a main hydraulic pump connected for supplying hydraulic fluid to said steering control valves, said steering valves each being changeable between a supply condition in which the associated clutch is connected with the main pump and a neutral condition in which the associated clutch is not so connected, and a further hydraulic pump connected to said steering valves to top-up each hydraulic line with hydraulic fluid whenever the respective steering valve is in its neutral condition.

By topping up the hydraulic lines in the above manner each time the associated steering control valve is in its neutral condi tion it is ensured that a quick response is obtained from each steering clutch on each occasion that the associated steering control valve is changed to its supply position.

In a circuit in accordance with the present invention for use in a vehicle in which the tracks are driven via a torque converter, said further hydraulic pump may be arranged to be driven from the torque converter impeller.

In such an arrangement said further pump may be a scavenge pump which draws fluid from a sump of the torque converter.

In a circuit in accordance with the present invention in which oil is the hydraulic fluid, said circuit may include means connected with said further pump for spraying oil onto the steering clutches.

The spraying means may also be arranged to spray oil onto at least one of the following namely brakes of the vehicle, bevel gears forming part of a drive train to the tracks, and power take-off shaft bearings.

In a circuit for use in a vehicle having a power shift transmission and a transmission sump which collects oil draining from the power shift transmission, steering clutches and bevel gears, said circuit may include a fluid connection between said transmission sump and torque converter sump.

One embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings of which: Figure 1 is a diagrammatic representation of the transmission of a tracked vehicle together with the necessary hydraulic control circuit and the circuit according to the invention and Figure 2 is a hydraulic circuit diagram showing in greater detail the hydraulic circuit according to the invention.

Referring to Figure 1 of the drawings in a tracked vehicle an engine 1 drives a torque converter 2 which in turn drives through shaft 3 and power shift 4, a spiral bevel gear 5 meshing with crown wheel 6 keyed to drive shaft 7 by means of which the tracks (not shown) of the vehicle are driven.

A main hydraulic pump 8 is driven by the torque converter 2 and supplied pressurized hydraulic fluid (oil in the example described) to a clutch control valve in the power shift 4 and to steering control valve housing 9 through a pressure regulating system 10. Oil is drawn by the pump 8 from the pump 11 of the transmission housing 12.

The torque converter 2 is connected to the pressure regulating system 10 for control of inlet pressure and to cooling and regulating system 13 for control of outlet pressure, excess oil being released to the torque converter sump 14 through oil line 35. Oil line 34 provides for lubrication of clutches in power shift 4.

A further or scavenge pump 15 driven by the torque converter 2 is mounted upon and draws oil from the torque converter sump 14, the sump 14 being incorporated in a housing (not shown) for the torque converter. The pump 15 passes oil through lines 16 and 17 to two steering control valves 20 and 21 mounted in the housing 9.

Each of the steering control valves 20 and 21 is changeable between a neutral condition 20a, 21 a respectively and a supply condition 20b, 21b respectively.

When either steering control valve 20, 21 is in its neutral condition the line 22, 23 which connects the respective steering clutch 24, 25 with its associated steering control valve is kept topped up with oil via lines 17 and 16.

This ensures that when either steering control valve is changed to its supply condition a quick response is obtained from the associated steering clutch.

In the installation illustrated the lines 22, 23 will supply oil to piston and cylinder assemblies in the steering clutches which when pressurized disengages the clutches to disengage power from the associated vehicle tracks. However, it will be understood that the piston and cylinder assemblies could be arranged, particularly on smaller tracked vehicles, to engage the associated steering clutches to direct power to the associated tracks.

The oil spillage from the clutches 24 and 25 flows into the sump 11 which is interconnected with the sump 14.

The pump 15 is connected by line 16 and line 26 to spray lines 27 and 28 terminating in nozzles which spray oil onto the clutches 24 and 25. Pressure for operation of the oil spray and for maintaining oil in the lines 22 and 23 is controlled by a pressure relief valve 29 exhausing into sump 11. Oil is similarly sprayed onto the bevel gears 5 and 6, band brakes 40 and power take off shaft bearings 41 through other oil spray lines shown diagrammaticallyin Figure 2 at 42, 43 and 44.

The torque converter sump 14 is interconnected by oil line 30 with the sump 11 and by oil line 31 to the power shift 4 whilst the main pump 8 is connected on the suction side to -the transmission sump 11 by oil line 32 and on the outlet side to the steering valve housing 9 through oil line 33. Thus oil circulates throught the torque converter 2, power shift 4, main pump 8, the piston and cylinder arrangement of the steering clutches 24 and 25, auxiliary pump 15, bevel gears 5 and 6, the transmission sump 11 and torque converter sump 14.

In operation, the auxiliary pump 15 supplies oil from the torque converter sump 14 through oil line 16 at a pressure of 0.5 bar, which is insufficient to actuate clutches 24 and 25, determined by relief valve 29. In the neutral position of either of the steering valves 20 or 21, the oil from the pump 15 passes into the oil line 22 or 23 and hence to the piston and cylinder assemblies of clutches 24 or 25 and thereby maintains the oil lines 22 and 23 full of oil thus topping-up the clutches 24 and 25, whilst high pressure oil from main pump 8 through oil line 33 is cut off by the steering valves 20 and 21.

Moving either of the steering valves from the neutral condition to the supply condition permits high pressure oil from main pump 8 to flow through oil line 33 into either oil line 22 or 23 to disengage clutches 24 or 25.

Maintaining oil in the lines 22 and 23 whilst the valves 20 and 21 are in the neutral condition ensures that there is no lag in operation of the clutches 24 and 25 on admission of high pressure oil by movement of valves 20 and 21.

Oil from the pump 15 flows through oil line 26 independently of the flow through the lines 22 and 23 to pass through spray links 27 and 28 and continuously spray with oil the clutches 24 and 25 and other components such as band brakes 45, bevel gears 46 and power take-off shaft bearings 41 through appropriately located nozzles 43, 42 and 44.

Oil draining off these components flows into the transmission sump 11 which also serves the power shift 4, and through oil line 30 to torque converter sump 14 for re-use by auxiliary pump 15 or through oil line 32 to the main pump.

The various oil lines mentioned above may be either separate pipes or passageways formed in or between housings.

It will thus be seen from the above that the invention provides an arrangement for overcoming the operation lag found in prior art steering mechanisms.

WHAT WE CLAIM IS: 1. Ahydrauliccircuitfora steering mechanism of a tracked vehicle having a pair of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. converter 2 which in turn drives through shaft 3 and power shift 4, a spiral bevel gear 5 meshing with crown wheel 6 keyed to drive shaft 7 by means of which the tracks (not shown) of the vehicle are driven. A main hydraulic pump 8 is driven by the torque converter 2 and supplied pressurized hydraulic fluid (oil in the example described) to a clutch control valve in the power shift 4 and to steering control valve housing 9 through a pressure regulating system 10. Oil is drawn by the pump 8 from the pump 11 of the transmission housing 12. The torque converter 2 is connected to the pressure regulating system 10 for control of inlet pressure and to cooling and regulating system 13 for control of outlet pressure, excess oil being released to the torque converter sump 14 through oil line 35. Oil line 34 provides for lubrication of clutches in power shift 4. A further or scavenge pump 15 driven by the torque converter 2 is mounted upon and draws oil from the torque converter sump 14, the sump 14 being incorporated in a housing (not shown) for the torque converter. The pump 15 passes oil through lines 16 and 17 to two steering control valves 20 and 21 mounted in the housing 9. Each of the steering control valves 20 and 21 is changeable between a neutral condition 20a, 21 a respectively and a supply condition 20b, 21b respectively. When either steering control valve 20, 21 is in its neutral condition the line 22, 23 which connects the respective steering clutch 24, 25 with its associated steering control valve is kept topped up with oil via lines 17 and 16. This ensures that when either steering control valve is changed to its supply condition a quick response is obtained from the associated steering clutch. In the installation illustrated the lines 22, 23 will supply oil to piston and cylinder assemblies in the steering clutches which when pressurized disengages the clutches to disengage power from the associated vehicle tracks. However, it will be understood that the piston and cylinder assemblies could be arranged, particularly on smaller tracked vehicles, to engage the associated steering clutches to direct power to the associated tracks. The oil spillage from the clutches 24 and 25 flows into the sump 11 which is interconnected with the sump 14. The pump 15 is connected by line 16 and line 26 to spray lines 27 and 28 terminating in nozzles which spray oil onto the clutches 24 and 25. Pressure for operation of the oil spray and for maintaining oil in the lines 22 and 23 is controlled by a pressure relief valve 29 exhausing into sump 11. Oil is similarly sprayed onto the bevel gears 5 and 6, band brakes 40 and power take off shaft bearings 41 through other oil spray lines shown diagrammaticallyin Figure 2 at 42, 43 and 44. The torque converter sump 14 is interconnected by oil line 30 with the sump 11 and by oil line 31 to the power shift 4 whilst the main pump 8 is connected on the suction side to -the transmission sump 11 by oil line 32 and on the outlet side to the steering valve housing 9 through oil line 33. Thus oil circulates throught the torque converter 2, power shift 4, main pump 8, the piston and cylinder arrangement of the steering clutches 24 and 25, auxiliary pump 15, bevel gears 5 and 6, the transmission sump 11 and torque converter sump 14. In operation, the auxiliary pump 15 supplies oil from the torque converter sump 14 through oil line 16 at a pressure of 0.5 bar, which is insufficient to actuate clutches 24 and 25, determined by relief valve 29. In the neutral position of either of the steering valves 20 or 21, the oil from the pump 15 passes into the oil line 22 or 23 and hence to the piston and cylinder assemblies of clutches 24 or 25 and thereby maintains the oil lines 22 and 23 full of oil thus topping-up the clutches 24 and 25, whilst high pressure oil from main pump 8 through oil line 33 is cut off by the steering valves 20 and 21. Moving either of the steering valves from the neutral condition to the supply condition permits high pressure oil from main pump 8 to flow through oil line 33 into either oil line 22 or 23 to disengage clutches 24 or 25. Maintaining oil in the lines 22 and 23 whilst the valves 20 and 21 are in the neutral condition ensures that there is no lag in operation of the clutches 24 and 25 on admission of high pressure oil by movement of valves 20 and 21. Oil from the pump 15 flows through oil line 26 independently of the flow through the lines 22 and 23 to pass through spray links 27 and 28 and continuously spray with oil the clutches 24 and 25 and other components such as band brakes 45, bevel gears 46 and power take-off shaft bearings 41 through appropriately located nozzles 43, 42 and 44. Oil draining off these components flows into the transmission sump 11 which also serves the power shift 4, and through oil line 30 to torque converter sump 14 for re-use by auxiliary pump 15 or through oil line 32 to the main pump. The various oil lines mentioned above may be either separate pipes or passageways formed in or between housings. It will thus be seen from the above that the invention provides an arrangement for overcoming the operation lag found in prior art steering mechanisms. WHAT WE CLAIM IS:

1. Ahydrauliccircuitfora steering mechanism of a tracked vehicle having a pair of

tracks driven by a prime mover via hydraulic steering clutches, said circuit including a pair of steering control valves, hydraulic lines connecting each steering valve with a respective one of said steering clutches, a main hydraulic pump connected for supplying hydraulic fluid to said steering control valves, said steering valves each being changeable between a supply condition in which the associated clutch is connected with the main pump and a neutral condition in which the associated clutch is not so connected, and a further hydraulic pump connected to said steering valves to top-up each hydraulic line with hydraulic fluid whenever the respective steering valve is in its neutral condition.

2. A circuit according to claim 1 for use in a vehicle in which the tracks are driven via a torque converter, said further hydraulic pump being arranged to be driven from the torque converter impeller.

3. A circuit according to claim 2 in which said further pump is a scavenge pump which draws fluid from a sump of the torque converter.

4. A circuit according to claim 3 in which said further pump is mounted on the torque converter sump.

5. A circuit according to any one of claims 1 to 4 in which oil is the hydraulic fluid, said circuit including means connected with said further pump for spraying oil onto the steering clutches.

6. A circuit according to claim 5 in which the spraying means is also arranged to spray oil onto at least one of the following namely brakes of the vehicle, bevel gears forming part of a drive train to the tracks, and power take-off shaft bearings.

7. A circuit according to claims 3 and 5 for use in a vehicle having a power shift transmission and a transmission sump which collects oil draining from the power shift transmission, steering clutches and bevel gears, said circuit including a fluid connection between said transmission sump and torque converter sump.

8. A hydraulic circuit for a steering mechanism of a tracked vehicle, said circuit being constructed and arranged substantially as hereinbefore described with reference to and as shown in the accompanying drawings.