Field of the Invention

The present invention relates to a vehicle having a hydraulic pump for a hydraulic circuit which is driven by the vehicle transmission connected using a gearbox, and a gearbox for such a vehicle.

Background of the Invention

In many vehicles, in particular agricultural tractors, hydraulic flow may be provided by a pump coupled to the vehicle transmission. Through a gear-driven shaft, the hydraulic pump rotates at the speed of the engine with a fixed ratio to produce flow of hydraulic fluid. Such a known configuration is illustrated in the schematic view of Fig. 2(a), wherein a hydraulic pump 24 is connected to a transmission 22 driven by engine 20. Different hydraulic applications can have varying hydraulic flow requirements. Pumps having a high hydraulic flow supply are used to ensure acceptable operational performance. In order to achieve higher flow supply, there are two generally accepted prior art approaches: (a) increase pump displacement, and (b) increase pump speed. However, both approaches present difficulties if used on modern vehicles.

For the first approach, increasing the displacement of the pump leads to increased space and cost requirements for the pump in the overall vehicle construction.

With the second approach, increasing the pump speed can increase the wear-and-tear for a pump driven by a vehicle transmission. For example, for an agricultural tractor, the tractor engine can often reach speeds greater than 2600 rpm, e.g. during a downhill ride. A pump coupled to such an engine via a gear ratio will likely be rotated at speeds in excess of the specified operating conditions for the pump, with potential damage to the pump components. Similarly, if the engine is operating in a high idle state during working condition, the rpm of the engine may be at around 2200 rpm, resulting in a high flow speed for the connected pump. A possible solution to these issues is to provide oversized flow lines and valves. However, this results in increased space and cost requirements.

In a further consideration, due to increased requirements for emission control and efficient operation of vehicle systems, there is a desire to provide systems having reduced fuel consumption in general. For hydraulic flow systems, this results in a desire for a system having a high flow at a relatively low engine speed. It is an object of the invention to provide a vehicle system that addresses the above issues. Summary of the Invention

Accordingly, there is provided a vehicle, preferably an agricultural tractor, comprising: an engine,

a transmission driven by the engine, and

a hydraulic pump for pumping fluid in a hydraulic circuit of the vehicle,

wherein the vehicle further comprises

a gearbox arranged between the transmission and the hydraulic pump, the gearbox having an input driven by the transmission and an output driving the hydraulic pump, the gearbox having at least one integrated clutch arranged to select a gear ratio between the output and the input,

wherein the gearbox is adjustable between at least:

a first state where the output is run at a first gear ratio of the input, and a second state where the output runs at a second gear ratio of the input, the second gear ratio greater than the first gear ratio. Gear ratio is understood as the ratio of the input to the output for a gear train. A low gear ratio means that a relatively small rotation of the input results in a relatively large rotation of the output, and vice versa. It will be understood that the gearbox comprises gear trains arranged to provide suitable gear ratios between the input and output of the gearbox. By providing a first relatively low gear ratio, the hydraulic pump can be operated at relatively high pump speed for a relatively low input speed received from the engine. Accordingly, efficient vehicle operation can be ensured, e.g. during periods of low engine speed. Providing a second gear ratio, higher than the first, allows for the pump to be operated during periods of high engine speed at the higher gear ratio. As a result, the operation of the hydraulic pump during such periods of high engine speed will not exceed pump specifications, and prevent damage to the pump. In one aspect, the gearbox is provided as a part of the transmission, e.g. as a component internal of the housing of the transmission. In an alternative aspect, the gearbox is provided as a part of the hydraulic pump, e.g. as a component internal of the housing of the pump.

In such configurations, the gearbox may be integrated into the design and manufacture of either of these vehicle components.

In a further alternative aspect, the gearbox is provided as a separate component having a separate housing. Such a separate component may be installed during initially manufacture and assembly of the vehicle, or may be retrofitted to an existing vehicle by reconfiguring the vehicle layout by positioning the gearbox between the transmission and hydraulic pump.

Preferably, the input and output of the gearbox are coaxial.

As the input and output shafts of the gearbox are coaxial, accordingly the gearbox may be relatively easily incorporated into a pre-existing vehicle design without requiring significant modification of the connections between the vehicle transmission and the hydraulic pump. It will be understood that the hydraulic pump may comprise a plurality of separate pumps, or a pump stack.

Preferably, the vehicle comprises an Engine Control Unit (ECU), wherein the gearbox is controlled by the ECU.

Preferably, the gearbox is controlled such that:

for a relatively low engine speed, the gearbox is operated in said first state, and for a relatively high engine speed, the gearbox is operated in said second state. Preferably, the gearbox is controlled such that:

when engine speed is less than approximately 2000 rpm, the gearbox is operated in said first state, and

when engine speed is greater than approximately 2000 rpm, the gearbox is operated in said second state.

Preferably, the at least one clutch is driven hydraulically. In a preferred embodiment, the second gear ratio is approximately 1 :1 .

In a preferred aspect, the gearbox comprises a plurality of gear trains arranged to provide a range of gear ratios between the output and the input. It will be understood that the gearbox may be controlled to select the gear ratio most appropriate for the vehicle operating conditions.

There is also provided a gearbox for a hydraulic pump of an agricultural vehicle, the gearbox comprising:

an input to receive a driving output from a transmission;

an output to drive a hydraulic pump for a hydraulic circuit; and

at least one integrated clutch arranged to select a gear ratio between the output and the input,

wherein the gearbox is adjustable between at least:

a first state where the output is run at a first gear ratio of the input, and a second state where the output runs at a second gear ratio of the input, the second gear ratio greater than the first gear ratio.

The gearbox can be provided as a retrofit solution for an existing vehicle, to improve the performance efficiency of the hydraulic circuit of the vehicle.

There is also provided a vehicle transmission having an integrated gearbox for a hydraulic pump of an agricultural vehicle, as described above. Additionally or alternatively, there is also provided a hydraulic pump for an agricultural vehicle having an integrated gearbox for connection to a vehicle transmission, as described above.

Detailed Description of the Invention

Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Fig. 1 is an illustration of an agricultural tractor;

Fig. 2(a) is an illustration of the known configuration of a vehicle hydraulic pump and associated engine and transmission;

Fig. 2(b) is an illustration of a configuration of a vehicle hydraulic pump and associated engine and transmission according to an aspect of the invention; Fig. 3 shows a configuration of a first embodiment of a gearbox of the invention; Fig. 4 shows a configuration of a second embodiment of a gearbox of the invention; and

Fig. 5 shows a configuration of a third embodiment of a gearbox of the invention.

In Fig. 1 , an agricultural tractor is indicated at 10. The tractor 10 comprises front wheels 12, rear wheels 14, an engine section 16 and a cab section 18. An engine 20 is provided in the engine section 16, which is connected to the vehicle transmission 22 (shown in Fig. 2(b)). The tractor 10 comprises an Engine Control Unit (ECU, not shown), which is configured to control the operation of the engine 20 of the tractor 10, as well as any additional vehicle systems, based on input received from the tractor operation and/or any tractor sensor systems.

With reference to Fig. 2(b), the tractor 10 further comprises a hydraulic pump 24, which is coupled to a hydraulic circuit (not shown) for providing hydraulic fluid flow throughout the tractor 10. The pump 24 is connected to the vehicle transmission 22 via a clutchable gearbox 26.

The gearbox 26 is arranged to provide a selectable gear ratio between the output of the transmission 22, and the input to the hydraulic pump 24. When the engine 20 and the transmission 22 are operating at a relatively low rpm level, the gear ratio provided by the gearbox 26 can be arranged such that the pump 24 is driven at a comparatively high speed. When the engine 20 and the transmission 22 are operating at a relatively high level of rpm, the gear ratio of the gearbox 26 can be changed, such that the pump 24 is driven at a speed close to that of the transmission, such that over-speeding of the pump 24 and any possible damage to pump components is prevented.

In a first embodiment, the gearbox 26 comprises a single clutch and a single gear ratio solution. The gearbox 26 is configured to operate in a first state where the output is run at a first gear ratio of the input, and a second state where the output runs at a second gear ratio of the input, where the second gear ratio is greater than the first gear ratio. Additional embodiments of the invention may comprise a plurality of separate gear ratio solutions, allowing for a range of different gear ratios between the transmission 22 and the pump 24. By providing a first relatively low gear ratio, the hydraulic pump can be operated at relatively high pump speed for a relatively low input speed received from the engine. Accordingly, efficient vehicle operation can be ensured, e.g. during periods of low engine speed. Providing a second gear ratio, higher than the first, allows for the pump to be operated during periods of high engine speed at the higher gear ratio. As a result, the operation of the hydraulic pump during such periods of high engine speed will not exceed pump specifications, and prevent damage to the pump.

The operation of the gearbox 26 may be controlled by the ECU, wherein the adjustment of the clutch between the separate configurations is based on the rpm of the engine. In one example embodiment, the ECU is configured such that when engine speed is less than approximately 2000 rpm, the gearbox 26 is operated in the first state, and when engine speed is greater than approximately 2000 rpm, the gearbox is operated in the second state.

In a preferred aspect, the gearbox 26 is arranged to enable the pump 24 to run either (i) at the speed of the standard installation (i.e. the fixed ratio of the transmission), or (ii) at a higher speed (i.e. the ratio of the transmission times the ratio of the dedicated gear box) to provide more flow capacity of the pump 24. In one aspect, the gearbox 26 is arranged to drive the pump 24 to provide approximately 200 Ipm flow at approximately 1500-1600 rpm engine speed. In the embodiment illustrated in Fig. 2(b), the gearbox 26 is provided as a separate component arranged between the transmission 22 and the pump 24, where the gearbox 26 may have a separate housing, mounting flanges, etc. Such a solution may be produced separately from the tractor 10, which allows for the gearbox 26 to provide a retrofit solution for an existing tractor.

In alternative embodiments, the gearbox may be provided as an integral part of the vehicle transmission 22 or the hydraulic pump 24, e.g. as an internal component located within the component housing. In this case of such configurations, the gearbox may be integrated into the design and manufacture of either of these vehicle components.

The gearbox 26 is preferably provided as a hydraulically-actuated gearbox, wherein the clutch is controlled via hydraulic actuators, which may be operated by a solenoid or other suitable valve system controlled by the vehicle ECU. Examples of possible configurations of the gearbox 26 are shown in Figs. 3-5. It will be understood that other configurations of gearbox may be utilised in the system of the invention. With regard to the embodiments shown in Figs. 3-5, the gearbox 26 comprises an input shaft 28 and an output shaft 30. The input shaft 28 and output shaft 30 are coaxially arranged on opposed sides of the gearbox 26. As the shafts 28,30 are coaxial, the gearbox 26 may be relatively easily incorporated into a pre-existing vehicle layout, without requiring significant adjustment or rearrangement of the vehicle components, e.g. the preexisting connection between the vehicle transmission 22 and the hydraulic pump 24.

In the embodiment of Fig. 3, the input shaft 28 terminates at sun gear 32 which engages planet gear 34. The output shaft 30 terminates at sun gear 36 which engages planet gear 38. The planet gears 34,38 are provided on common carrier 40. The carrier 40 is provided in clutchable engagement with output shaft 30 via clutch plates 42. The clutch plates 42 are biased towards engagement of the carrier 40 with the output shaft 30 using spring bias 44. The gearbox 26 further comprises actuator 46 which is arranged to act on clutch plates 48 which are further connected to the carrier 40. Clutch plates 48 provide for selectable engagement of the carrier 40 with the frame of the gearbox, indicated at 50, to fix the carrier 40 with the frame 50.

For operation of the embodiment of Fig. 3, if the actuator 46 is OFF, clutch plates 48 are not engaged, and the carrier 40 is free to rotate. The biasing of the clutch plates 42 causes the output shaft 30 to rotate with the carrier 40. Accordingly, for an initial gear ratio of 1 :1 , the output shaft 30 will rotate at the same speed as the input shaft 28.

If the actuator 46 is ON, clutch plates 48 are engaged and overcome the biasing strength of the spring bias 44, such that the carrier 40 is held against the frame 50. Accordingly, the speed of the output shaft 30 is determined by the gear ratio between the planet gears 34,38.

In the embodiment of Fig. 4, the input shaft 28 terminates at sun gear 52 which engages planet gear 54. Planet gear 54 is provided on carrier 56, which is connected to the output shaft 30. Planet gear 54 further engages with ring gear 58, which is clutchably engageable with the input shaft 28 via clutch plates 60. The clutch plates 60 are biased towards engagement with the input shaft 28 using spring bias 62. The gearbox 26 further comprises actuator 64 arranged to act on clutch plates 66 which are further coupled to the ring gear 58. Clutch plates 66 provide for selectable engagement of the ring gear 58 with the frame of the gearbox, indicated at 68, to fix the ring gear 58 with the frame 68. For operation of the embodiment of Fig. 4, if the actuator 64 is OFF, clutch plates 66 are not engaged and the ring gear 58 is connected to the input shaft 28. The planet gear 54 is locked, and the carrier 56 and connected output shaft 30 rotate with the input shaft 28. If the actuator 64 is ON, clutch plates 66 are engaged and overcome the biasing strength of the spring bias 62, such that the ring gear 58 is released from engagement with the input shaft 28, the ring gear 58 held against the frame 68. Accordingly, the output shaft 30 is rotated via the gear ratio between sun gear 52 and planet gear 54. The embodiment of Fig. 5 utilises a dog-clutch-style arrangement. Input shaft 28 terminates in first dog clutch plate 70. The input shaft 28 is further provided with sun gear 72 which engages with planet gear 74. Planet gear 74 is coupled to a further sun gear 76 via a compound planet gear connection. Sun gear 76 is connected to second dog clutch plate 78.

The output shaft 30 terminates in dog clutch carrier 80, which is moveable between a first position in engagement with the first dog clutch plate 70 and a second position in engagement with the second dog clutch plate 78. The gearbox 26 further comprises a two-state hydraulic valve 82 in connection with a hydraulic cylinder 84. The cylinder 84 comprises a central bore 86 having a piston 88 located therein. The bore 86 is shaped such that a relatively large chamber 90 is defined on one side of the piston 88 in the bore 86, when compared to the chamber 92 defined on the opposite side of the piston 88. The valve 82 is arranged to selectively supply fluid to the larger chamber 90, to control the pressure difference seen across the piston 88.

The piston 88 is connected to the dog clutch carrier 80, wherein movement of the piston 88 in the bore 86 is translated into movement of the dog clutch carrier 80 between the first and second positions.

For operation of the embodiment of Fig. 5, if the valve 82 is ON, as shown in the configuration of Fig. 5, fluid is supplied to both the relatively large chamber 90 and the relatively small chamber 92. The fluid supplied to the large chamber 90 pushes the piston 88 towards the small chamber 92. Accordingly, the piston 88 moves the dog clutch carrier 80 to the second state, where the dog clutch carrier 80 of the output shaft 30 is in engagement with the second dog clutch plate 78. As a result, the output shaft 30 is connected to the input shaft 28 through the geared connection 72,74,76. The output shaft 30 rotates via the gear ratio provided by the different gears 72,74,76.

If the valve 82 is OFF, no fluid is supplied to the large chamber 90. As a result, the pressure of the fluid supplied in the small chamber 92 pushes the piston 88 towards the large chamber 90. Accordingly, the piston 88 moves the dog clutch carrier 80 to the first state, where the dog clutch carrier 80 of the output shaft 30 is in engagement with the first dog clutch plate 70. The output shaft 30 is in direct engagement with the input shaft 28, and as a result the output shaft 30 rotates in a 1 :1 engagement with the input shaft 28.

It will be understood that the actuators 46,64 or valve 82 may comprise any hydraulic actuator or suitable valve, which may be controlled using a solenoid or other device regulated by the vehicle ECU. The system of the invention presents a number of advantages over the prior art:

It enables higher levels of hydraulic flow using standard pump sizes;

Lower engine speed enables fuel saving, lower emission and noise reductions; The integrated design and small form factor results in a low impact on standard version designs, and acceptable space constraints;

A retrofittable solution allows for the invention to be easily rolled-out to existing tractors as a method of improving tractor efficiency; and

The gearbox eliminates the drawbacks of a higher ratio in the vehicle transmission. The invention is not limited to the embodiments described herein, and may be modified or adapted without departing from the scope of the present invention.