DESC:HYBRID LOAD SENSING HYDRAULIC CIRCUIT FOR BACKHOE LOADER MACHINES

FIELD OF INVENTION
The present invention is directed to mechanical backhoes, and relates specifically to new improved hybrid load sensing hydraulic circuit using gear pump & open centre valves which will save energy, fuel consumption and reduce overall hydraulic oil system capacity.
BACKGROUND OF THE INVENTION
The conventional hydraulic circuit of backhoe loader generally powered by 76 hp/90 hp engine machines as depicted in schematic diagram in figure 1.
In the existing hydraulic circuit the circuit uses a tandem gear pump with two pressure line outlets with conventional loader (2/3 spool) and backhoe valve (6/7 spool) that can handle nominal flow of 160 l/min and a max operating pressure of 320 bar as shown below in Figure 2
The existing loader valve has a feature of two pump unloader with electrically operated solenoid. The pressure settings of two pumps are 225 bar and 210 bar with main relief valve (MRV) system pressure setting of 225 bar.
In the existing circuit with double pump options, fuel saving is achieved:
1) Whenever system pressure crosses 210 bar in loader and backhoe operation, one pump is connected to tank and thus resulting in engine unload & thus resulting in fuel saving.
2) When machine is in travel mode, one pump can be dumped manually by electrical switch provided inside cabin side dashboard, thus power & fuel saving in travel mode.
The present invention is related to mechanical backhoes, and specifically to new improved hybrid load sensing hydraulic circuit using gear pump and open centre valves which will save energy, fuel consumption and reduce overall hydraulic oil system capacity. The new loader valve arrangement mainly involves first section of pump delivery herein denotes as P1, enters loader valve block at 2 pump unloading section; and second section of pump delivery herein denotes as P2, enters loader valve block at IC section. Both P1 and P2 are mix/added in IC section of loader valve.
SUMMARY AND OBJECTIVE OF INVENTING NEW HYBRID LOAD SENSING CIRCUIT
The main objective of the present invention is to provide an improved hybrid load sensing hydraulic circuit for backhoe loader machines
It is an objective of the present invention to provide an hydraulic circuit in backhoe loader that saves power, lowers fuel consumption & reduces overall hydraulic oil in the system.
It is an objective of the present invention wherein, a new circuit can easily save 5-10% (0.25-0.5 litres) fuel saving in backhoe operations with respect to conventional hydraulic circuit.
It is another objective of the present invention wherein, a new circuit can easily save 15-20% (0.75-1.0 litres) fuel saving in road running and loader operations with respect to conventional hydraulic circuit.
Yet another objective of the present invention wherein, a new circuit that can easily reduce 12-16% (25-35 litres) of overall hydraulic oil quantity from overall system capacity.
It is another object of the present invention wherein, the response time of backhoe operations will improve in resulting in less fatigue to operator while operating backhoe levers.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 depicts the schematic diagram of conventional hydraulic circuit of backhoe loader generally powered by 76 hp/90 hp engine machines.
Figure 2 depicts the schematic diagram of a tandem gear pump with two pressure line outlets with conventional loader (2/3 spool) and backhoe valve (6/7 spool) that can handle nominal flow of 160 l/min and a max operating pressure of 320 bar.
Figure 3 depicts the schematic diagram of the new hybrid circuit (open center load sensing) for backhoe loader uses tandem gear pump with two pump outlets.
Figure 4 depicts the schematic diagram of Working Principle of New Hybrid New Load Sensing Circuit.
DETAIL DESCRIPTION OF THE INVENTION
The new hybrid circuit (open center load sensing) for backhoe loader uses tandem gear pump with two pump outlets as shown in figure 3.
The changes are being carried out in1 loader control valve by adding an inlet compensator (IC) in Inlet section.
The new loader valve arrangement comprises of two pump delivery sections P1 and P2.
• P1 (first section of pump delivery) enters loader valve block at 2 pump unloading section
• P2 (second section of pump delivery) enters loader valve block at IC section
• P1 and P2 mix/added in IC section of loader valve
The New Valves Configuration comprises of two valves namely Loader Control Valve and Excavator Control Valve.
The Loader Control Valve comprises of the following:
• 2 pump unloader with solenoid and Inlet Compensator (IC)
• Nominal flow of 160 l/min and a max operating pressure of 320 bar
The Excavator Control Valve comprises of the following:
• Nominal flow of 160 l/min and a max operating pressure of 320 bar
• Electric side shift provided in the outlet cover
The proposed invention herein discloses the working principle of new hybrid load sensing circuit, according to the said invention, for backhoe loader, reduction in fuel consumption can be achieved especially by reducing a load of a hydraulic pump during execution of a work with a backhoe or in loader reaches a) peak pressure or when there is no work or load on hydraulic implements, like machine running on road or b) machine running at idle or at full throttle or part throttle.
As disclosed in figure 4 a hydraulic system for a machine having a gear pump, a steering circuit and first and second hydraulic implements, e.g., a hydraulic loader and a backhoe, powered by first and second valve sections, respectively.
1) In the neutral position:
In neutral position flow from first section gear pump reaches priority valve cum steering circuit and then excess flow passes to the first valve P1 of (loader). The flow from second section of gear pump joins the first valve section at P2 port. The combined flow reaches inlet section of inlet compensator and is now available for loader operation.
When there is no flow requirement at first valve, only 45 liters of flow passes through neutral gallery to HPCO and rest all the flow is dumped to tank thus unloading the engine and saving fuel.
Compensator relief valve is normally closed type. Orifice (8 mm dia.) is added in the compensator line of loader valve which maintains a delta pressure drop of 1.5 bars across the port and will not open the Inlet compensator relief valve and all the 45 lpm flow will pass through all the section of loader and backhoe valve neutral gallery.
Thus 45 lpm of flow will always be available to all the backhoe section and will avoid any time lag while operating any of the working section of Backhoe.
In case flow exceeds 45 lpm in neutral position, pressure drop across IC section increased and will open compensator relief valve proportionally beyond 1.5 bars present in IC section.
Further a bypass valve is added in the return circuit after return line filter. The bypass valve has a check valve setting of 2.5 bars, which ensures that 45-50 lpm of return flow always goes through oil cooler and rest bypasses and goes to tank. This allows ~50% flow to get cooled maintaining hydraulic oil temperature less than 80C and an optimum working temperature of 65C for efficient functioning of hydraulic system.
The pressure drop across the system at full throttle in the new circuit will be < 15 bar as compared to conventional ~40 bar pressure drop in the circuit. Thus an overall saving of 20~25 bar pressure drop resulting in a saving of 5~7 hp at rated combined pump flow of 117 lpm and ~14,040 BTU/hr of energy saving.
The fuel consumption saving considering saving of 20 bar pressure drop in the system at 117 lpm flow with an rated engine sfc (specific fuel consumption) of ~170 gm/hp-hr will result in 0.8-1.0 liters/hour of fuel savings in loader operations or road running operation easily.
Thus with new hydraulic circuit when machine is in idle state running at rated rpm (2200) the fuel consumption will get reduced by 0.8~1.0 liters/hour. Similarly when machine is travelling from one place to another and at rated rpm, with new circuit the fuel consumption will be reduced by 0.8~1.0 liters/hour.
Key highlights of Operation in Neutral/Idle rpm:
• Two pumps outlet flow is fed at two inlet ports P1 and P2 of loader control valve
• Flow through loader control valve neutral gallery to HPCO flow is only 45 lpm
• Flow from HPCO port to backhoe control valve neutral gallery is also 45 lpm
• Compensator at IC unloads combined flow>45 lpm of inlet ports P1 and P2 at unloader valve by opening the compensator proportionally beyond 1.5 bar.
2) Machine in operation:
Machine in operative position works in two modes namely Loader Valve Operation and Excavator Valve Operation. Both are explained herein below:
(A) Loader Valve Operation:
• When loader valve spool is operated, neutral gallery is closed, full flow of P1 and P2 is available at parallel gallery for loader valve operation
• If the flow is not utilised, it will be unloaded at load pressure instead of MRV pressure as in existing circuit thus saving fuel and power.
• At the end of stroke/dead end, LS valve opens and all oil is dumped through inlet compensator or when flow is not required, the P1 is unloaded through 2P unloader in loader control valve and thus reducing the load on engine.
(B) Excavator Valve Operation
• When Excavator is being operated the combined flow from pumps P1 & P2 ports will go to Excavator valve block (EVB) by passing the loader valve & is available for excavator operations
• Flow coming from P1 and P2 directly from IC section of Loader valve by-passing the working sections if excavator spool is operated thus improving response time and overall pressure drop across loader to backhoe valve.
• During the end of strokes where flow is not required much, the P1 flow is unloaded through the 2P unloader in loader sectional valve.
• The electric side shift lock is provided in the outlet of backhoe valve which is used when side shift of boom is to be carried out done by switching off the solenoid.
Key Highlights of New Hybrid Load Sensing Circuit
1. There is only a partial flow (45 litres) along the neutral gallery of the LVB and EVB (Excavator Valve Block) which minimises the pressure drop from P to T.
2. Adding inlet compensator will improve controllability of multiple functions.
3. Due to double pump option, fuel saving can be achieved whenever system pressure crosses 225 bar thus unloading two pumps.
4. In idle/no operation, neutral flow is 45 lpm only. Residual flow goes to tank by opening the compensator proportionally.
5. Due to unloading (with IC) of flow during travel/standby mode, pressure drop across circuit is limited to 15-20 bar against 35-40 bar in working condition & a saving of 14,040 BTU/hour of energy saving when no work is done by machine when running at rated rpm.
6. Due to lesser heat generation, overall hydraulic oil quantity can be reduced.
7. The new circuit can handle a max flow of 160 lpm and a system pressure upto 320 bar.
8. The flow management for the filter and cooling systems gets easier as it keeps constant the quantity of oil which flows through the neutral passage.
Scope of the present invention:
Although the invention has been described with reference to specific embodiments, this description is not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternate embodiments of the invention, will become apparent to persons skilled in the art upon reference to the description of the invention. It is therefore contemplated that such modifications can be made without departing from the spirit or scope of the present invention as defined.

CLAIMS:We Claim:
1. Hybrid Load Sensing Hydraulic Circuit For Backhoe Loader Machine, wherein said Hybrid Load Sensing Hydraulic Circuit mainly comprises of new hybrid circuit (open centre load sensing) for backhoe loader uses tandem gear pump with two pump outlets; wherein the working principle of new hybrid load sensing circuit, according to the said invention, for backhoe loader, reduction in fuel consumption can be achieved especially by reducing a load of a hydraulic pump during execution of a work with a backhoe or in loader reaches a) peak pressure or when there is no work or load on hydraulic implements, like machine running on road or b) machine running at idle or at full throttle or part throttle.
2. Hybrid Load Sensing Hydraulic Circuit For Backhoe Loader Machine, as claimed in claim 1, wherein The loader valve arrangement comprises of two pump delivery sections P1 and P2:
? P1 (first section of pump delivery) enters loader valve block at 2 pump unloading section;
? P2 (second section of pump delivery) enters loader valve block at IC section; and
? P1 and P2 mix/added in IC section of loader valve;
3. Hybrid Load Sensing Hydraulic Circuit For Backhoe Loader Machine, as claimed in claim 1, wherein the Valves Configuration comprises of two valves namely Loader Control Valve and Excavator Control Valve; wherein
(i) The Loader Control Valve comprises of the following:
? 2 pump unloader with solenoid and Inlet Compensator (IC), and
? Nominal flow of 160 l/min and a max operating pressure of 320 bar;
and
(ii) The Excavator Control Valve comprises of the following:
? Nominal flow of 160 l/min and a max operating pressure of 320 bar, and
? Electric side shift provided in the outlet cover.
4. Hybrid Load Sensing Hydraulic Circuit For Backhoe Loader Machine, as claimed in claim 1, wherein one preferred embodiment of said Hybrid Load Sensing Hydraulic Circuit is characterized in:
in the neutral position flow from first section gear pump reaches priority valve cum steering circuit and then excess flow passes to the first valve P1 of (loader), and the flow from second section of gear pump joins the first valve section at P2 port, and wherein the combined flow reaches inlet section of inlet compensator and is now available for loader operation; and
when there is no flow requirement at first valve, only 45 liters of flow passes through neutral gallery to HPCO and rest all the flow is dumped to tank thus unloading the engine and saving fuel; and wherein
the Compensator relief valve, normally closed type with Orifice (8 mm dia.) is added in the compensator line of loader valve which maintains a delta pressure drop of 1.5 bars across the port and will not open the Inlet compensator relief valve and all the 45 lpm flow will pass through all the section of loader and backhoe valve neutral gallery;
and therefore 45 lpm of flow will always be available to all the backhoe section and will avoid any time lag while operating any of the working section of Backhoe.
5. Hybrid Load Sensing Hydraulic Circuit For Backhoe Loader Machine, as claimed in claim 1, wherein in one preferred embodiment of the Backhoe loader machine operation of said Hybrid Load Sensing Hydraulic Circuit in Neutral/Idle rpm involves following steps:
? Two pumps outlet flow is fed at two inlet ports P1 and P2 of loader control valve
? Flow through loader control valve neutral gallery to HPCO flow is only 45 lpm
? Flow from HPCO port to backhoe control valve neutral gallery is also 45 lpm
? Compensator at IC unloads combined flow>45 lpm of inlet ports P1 and P2 at unloader valve by opening the compensator proportionally beyond 1.5 bar.
6. Hybrid Load Sensing Hydraulic Circuit For Backhoe Loader Machine, as claimed in claim 1, wherein in one preferred embodiment of the Hybrid Load Sensing Hydraulic Circuit in the Backhoe loader machine, the Loader Valve Operation includes following steps:
• When loader valve spool is operated, neutral gallery is closed, full flow of P1 and P2 is available at parallel gallery for loader valve operation;
• If the flow is not utilised, it will be unloaded at load pressure instead of MRV pressure as in existing circuit thus saving fuel and power;
• At the end of stroke/dead end, LS valve opens and all oil is dumped through inlet compensator or when flow is not required, the P1 is unloaded through 2P unloader in loader control valve and thus reducing the load on engine.
7. Hybrid Load Sensing Hydraulic Circuit For Backhoe Loader Machine, as claimed in claim 1, wherein in one preferred embodiment of the Hybrid Load Sensing Hydraulic Circuit in the Backhoe loader machine, the Excavator Valve Operation includes following steps:
• When Excavator is being operated the combined flow from pumps P1 & P2 ports will go to Excavator valve block (EVB) by passing the loader valve & is available for excavator operations;
• Flow coming from P1 and P2 directly from IC section of Loader valve by-passing the working sections if excavator spool is operated thus improving response time and overall pressure drop across loader to backhoe valve;
• During the end of strokes where flow is not required much, the P1 flow is unloaded through the 2P unloader in loader sectional valve.
8. Hybrid Load Sensing Hydraulic Circuit For Backhoe Loader Machine, as claimed in claim 1, wherein the electric side shift lock is provided in the outlet of backhoe valve which is used when side shift of boom is to be carried out done by switching off the solenoid; and wherein, the response time of backhoe operations will improve in resulting in less fatigue to operator while operating backhoe levers.
9. Hybrid Load Sensing Hydraulic Circuit For Backhoe Loader Machine, as claimed in claim 1, wherein one preferred embodiment of said Hybrid Load Sensing Hydraulic Circuit is characterized in:
(i) 5-10% (0.25-0.5 litres) fuel saving in backhoe operations with respect to conventional hydraulic circuits; and/or
(ii) 15-20% (0.75-1.0 litres) fuel saving in road running and loader operations with respect to conventional hydraulic circuit; and/or
(iii) Reduction of 12-16% (25-35 litres) of overall hydraulic oil quantity from overall system capacity.
10. Hybrid Load Sensing Hydraulic Circuit For Backhoe Loader Machines, as claimed in claim 1, wherein one preferred embodiment of said hybrid load sensing hybrid circuit is characterized in at least one of the followings:
• There is only a partial flow (45 litres) along the neutral gallery of the LVB and EVB (Excavator Valve Block) which minimises the pressure drop from P to T.
• Adding inlet compensator will improve controllability of multiple functions.
• Due to double pump option, fuel saving can be achieved whenever system pressure crosses 225 bar thus unloading two pumps.
• In idle/no operation, neutral flow is 45 lpm only. Residual flow goes to tank by opening the compensator proportionally.
• Due to unloading (with IC) of flow during travel/standby mode, pressure drop across circuit is limited to 15-20 bar against 35-40 bar in working condition & a saving of 14,040 BTU/hour of energy saving when no work is done by machine when running at rated rpm.
• Due to lesser heat generation, overall hydraulic oil quantity can be reduced.
• The new circuit can handle a max flow of 160 lpm and a system pressure upto 320 bar.
• The flow management for the filter and cooling systems gets easier as it keeps constant the quantity of oil which flows through the neutral passage.