FIELD OF THE INVENTION

The present invention relates to an off-road vehicle and/or construction, earthmoving equipment and particularly to a modified hydraulic control system used in off-road vehicle and/or construction, earthmoving equipment to regulate and control a discharge flow of a variable displacement hydraulic pump and more particularly to a modified hydraulic control system when an electric system get damaged or failed to work normally.

BACKGROUND OF THE INVENTION
Due to the huge size and weight of off-road or construction machine and functions need to perform while in the field and hence all off-road or construction machine generally well equipped with hydraulics system to control various operation of machine.
Hydraulic system further utilized in earthmoving or construction machine to convenience to operator to control various functions and also to provide better safety to operator and people working around the machine.

Various operations such as digging, excavation, loading, hammer, compaction etc. including an additional equipment used in such machine, requires a source of hydraulic fluid to perform these abovementioned operations. Hydraulic fluid is generally circulated by a pump driven by the machine engine.
Yet in another known system, to meet and optimize the flow demand of the hydraulic system, fixed displacement or variable displacement hydraulic pumps are used as power source with known pressure compensation methods. Such hydraulic systems requires high degree of complexity and very precise contamination control is required, again which is relatively difficult to maintain for many off-road machines working in extreme conditions of environment and put a significant cost impact and complexion in the whole system.
The hydraulic pump is used to supply flow against resistance given by application for circulating pressurised hydraulic fluid across various fluid circulation lines to perform various mentioned operations. The standard corresponding fluid pressure is required throughout these lines to perform such operation. However, if there has been least little pressure drop or more across the pressure line causes operation get stop or stall. There has been high probability that the hydraulic pump become disabled or is not operating.
In order to overcome a stalling effect which might result if hydraulic pumping system is disabled or not operating because of overloading, there is need to have an automatic hydraulic fluid pressure detection system to measure pressure across the hydraulic line and further gives instructions to regulate or manipulate the discharge rate of hydraulic fluid through the hydraulic pump.
In a conventional hydraulic system, the fixed or variable displacement hydraulic pumps are used as a power source for the hydraulic actuators. The fixed displacement hydraulic pump delivers a constant flow at particular pump shaft speed irrespective of the energy demand of the system whereas the variable displacement hydraulic pump delivers a variable flow with respect to the energy demand of the system. There is substantial loss of energy in such systems due to non-demanded energy supply.
A typical earthmoving or construction equipment whenever ran in neutral position, the whole hydraulic fluid pumped by the hydraulic pump circulated through neutral channel and again delivered it to hydraulic reservoir. During this position, the hydraulic pump is used to run into maximum shaft speed although no actuator was working hence there was zero utilization of energy. It causes substantial loss of energy.
To solve above mentioned problem mechanically controlled hydraulic pump system introduced in the conventional earthmoving or construction equipment. In such system, the discharge rate of hydraulic fluid by the hydraulic pump is controlled through the mechanical signals received from the orifice and relief valve installed on the hydraulic fluid lines.
However, the conventional mechanically controlled hydraulic pump system is very complex in construction and also less effective and observed as inefficient.
Another method has been developed which control hydraulic pump system electronically. However in such system when the electrical system get damaged or not working normally then hydraulic pump automatically goes to full stroke and in such situation if all hydraulic flow goes from neutral channel then due to high back pressure, very high amount of energy will get wasted.
To overcome abovementioned shortcoming and problems associated with conventional system, it is more desirable to achieve a control method that is more simple, fast and energy-efficient than previously known methods and solves or at least relieves some of the problems discussed above.
It is therefore an object of the present invention is to overcome one or more problems associated with the prior art.
The main objective of the present invention is to develop a modified hydraulic control system which work may work even if electronic circuit of such hydraulic control system get damaged or not working normally. A compensator is given at inlet of valve which can only allow certain amount of hydraulic flow to pass from neutral channel. If hydraulic flow exceeds the limit of compensator design then excess flow will be dumped to tank directly at inlet section without allowing flow to pass from neutral channel. Hence it shall be used to conserve the energy which may be lost due to damage of electronic system.
One another object of the present invention is to develop simple and electronically controlled hydraulic pump management system.
Yet another object of the present invention is to develop automatically controlled a modified hydraulic control system.
One more object of present invention is to develop a modified flow hydraulic control system which is user friendly and cost effective.
Yet another object of present invention is to supply required hydraulic fluid according to requirement and at pre-determined pressure.
A method according to an aspect of the present invention is also disclosed.
Further advantageous embodiments and further advantages of the invention emerge from the detailed description below.

SUMMARY OF THE INVENTION
The present invention is directed to a modified hydraulic control system for an earthmoving or construction machine to regulate and control a discharge of a variable displacement hydraulic pump.
An embodiment of the present invention is relates to modified hydraulic control system which is simple in construction, efficient, effective and robust in nature.
In a preferred embodiment of the present invention includes a variable displacement hydraulic pump unit mounted on a hydraulic fluid reservoir , an electronic control unit , a hydraulic pressure sensors to measure upstream and downstream hydraulic fluid pressure across the hydraulic pressure line, multiple control valves, multiple relief valves, multiple hydraulic actuators, multiple orifices, hydraulic fluid lines and compensator etc.
When the control valves are in neutral position, the whole hydraulic fluid pumped by the hydraulic pump mounted on hydraulic reservoir circulated through the hydraulic fluid line 15 and delivered again to hydraulic reservoir. The main actuator/s installed on the hydraulic system remains in inactive condition during this case. The downstream hydraulic pressure across the hydraulic fluid line 15 is measured by the downstream hydraulic pressure sensor and pressure sensor sends signal to ECU in voltage, further signal to pump given in terms of PWM signal.
During neutral position, whole hydraulic fluid gets transferred to reservoir through hydraulic fluid line 15 hence downstream hydraulic pressure sensor observes high pressure across the hydraulic fluid line due to high resistance of hydraulic fluid passing through the orifice then such output signal may be provided to ECU which further regulates the hydraulic pump. During high pressure phase ECU reduces the displacements of the hydraulic pump which further reduce the hydraulic fluid discharge rate.
When the control valves are start switching due to movement of spool in the control valve, during this case the main actuator/s installed on the hydraulic system gets into active condition. The downstream pressure sensor is mounted on the hydraulic fluid line 15 observe less pressure since spool in control valve switches which further partially and/or fully blocks the hydraulic fluid line 15 that results less flow to the orifice and relief valve. The downstream pressure sensor measure such less pressure and sends output signals in terms of PWM to the said ECU. In this case ECU actually increases the displacements of the hydraulic pump which further increase the hydraulic fluid discharge rate.
An another embodiment of the present invention includes the upstream pressure sensor installed in between hydraulic pump and the control valve on the hydraulic fluid line 15 to measure upstream hydraulic pressure across the hydraulic fluid line 15.
When any of the control valves of the hydraulic system are switched due to partial or full movement of spool, the hydraulic fluid gets supplied to the main actuator/s. The said upstream pressure sensor measure pressure across the hydraulic fluid line 15 and sends output signals to ECU. If the power demand of hydraulic pump is more than the power supplied by the engine then the displacement of hydraulic pump needs to be decreased to match with the engine power to avoid stalling and/or abnormality observed in the hydraulic system. The displacement of the hydraulic pump may be regulated by ECU. If upstream pressure sensor observe high pressure across the hydraulic fluid line 15 then displacement of the pump reduces accordingly on the basis of output signal received through upstream pressure sensor and with the help of ECU.
When above mentioned electronic system such as upstream or downstream sensing mechanism failed to work or electric lines got damaged in such situation then hydraulic pump automatically goes to full stroke and in such situation if all hydraulic flow goes from neutral channel then due to high back pressure, very high amount of energy will get wasted. A compensator is given at inlet of valve which can only allow certain amount of hydraulic flow to pass from neutral channel. If hydraulic flow exceeds the limit of compensator design then excess flow will be dumped to reservoir directly at inlet section without allowing flow to pass from the neutral channel.
An orifice is installed on the neutral channel to create pressure difference before and after the orifice. Multiple hydraulic pressure sensing units may be installed before and after an orifice to measure respective hydraulic fluid pressure before and after the orifice. The compensator is having biasing member which maintains initial or normal position of the compensator. Strength limit of biasing member is such that it can withhold pre-determined hydraulic pressure and if hydraulic fluid pressure starts increasing beyond the pre-determined hydraulic fluid pressure then the compensator starts pushing against the biasing member. Therefore bypass path gets open and excess hydraulic fluid will be dumped to reservoir directly without allowing hydraulic flow to pass from the neutral channel

BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects, features and advantages of the present invention explained with reference to the following drawings. A more detailed description of different exemplary embodiments of the invention will follow below.
In the drawings:
Figure 1 Illustrates a schematic representation showing a modified hydraulic control system during hydraulic fluid line 15 is active according to the present invention;
Figure 2 Illustrates a schematic representation showing a modified hydraulic control system during hydraulic fluid line 19 is active according to the present invention;
Figure 3 Illustrates a schematic representation showing a modified hydraulic control system during hydraulic fluid line 16 & 17 are active according to the present invention; and
Figure 4 Illustrates an another schematic representation showing a modified hydraulic control system during hydraulic fluid line 16 & 17 are active according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. The matters defined in the description, such as the detailed construction and elements, are nothing but specific details provided to assist those of ordinary skill in the art in a comprehensive understanding of the invention, and thus the present invention is not limited to thereto.
A modified hydraulic control system for an earthmoving or construction machine to regulate and control a discharge flow of a variable displacement hydraulic pump according to an embodiment of the present invention will be described hereinunder with reference to FIGS. 1 to 4.
As shown in FIG. 1, the modified flow type hydraulic control system 100 for an earthmoving or construction machine to regulate and control a discharge flow of a variable displacement hydraulic pump according to the first embodiment of the present invention is provided, which includes a variable displacement hydraulic pump unit 2 (hereinafter referred as hydraulic pump) mounted on a hydraulic fluid reservoir 1, an electronic control unit 3 (hereinafter referred as ECU), a hydraulic pressure sensors 4 & 12 to measure upstream and downstream hydraulic fluid pressure across the hydraulic pressure line 15, multiple control valves 7 & 8, multiple relief valves 6 & 14, multiple hydraulic actuators 9 & 10, and check valves 5,11 & orifice 13 , 21 & 22 , a compensator 23 , hydraulic fluid lines 15,16 17, 18 & 19 etc.
The hydraulic pump unit 2 for pumping hydraulic fluid from hydraulic reservoir driven by either machine engine, external engine, battery, external or internal power source, combination of either mentioned sources or any other means (which is not shown in fig.). The said hydraulic pump unit 2 pumps hydraulic fluid from the hydraulic reservoir 1 and supply it to hydraulic fluid line 15 as shown in FIG. 1.
The hydraulic pump unit 2 is connected to ECU 3 whereby the operation and manipulation of the hydraulic pump unit 2 is controlled by ECU 3 depending upon input signals received through upstream and downstream pressure sensors 4 & 12 respectively. The upstream pressure sensor 4 measures the hydraulic pressure across the hydraulic fluid lines 15, 16 & 17 before the hydraulic fluid passes through the control valve 7 whereas the downstream pressure sensor 12 measures the hydraulic pressure across the hydraulic fluid lines 15 after the hydraulic fluid passes through control valve 8. One or more hydraulic actuator may be installed on the said hydraulic fluid lines 15, 16 & 17. The check valves 5, 11 & orifice 13, 21, 22 may be installed on the said pressure lines 15, 16, 17, 18 & 19 before or after the control valves. The compensator 23 with biasing member is installed between neutral channel 15 & hydraulic pressure line 17. The multiple relief valves 6 & 14 may be installed on the said pressure lines 15, 16, 17, 18 & 19 as shown in FIG. 1.
The construction and functioning of hydraulic pump unit 2 may be same or different depending upon the requirements. The hydraulic fluid lines deliver hydraulic fluid to main actuator/s to perform various functions such as digging, excavating, loading, hammering, compaction etc.
The upstream and downstream pressure sensors provide output singles in terms of pulse width modulation (hereinafter referred as PWM) to ECU 3 which further control the hydraulic pump unit 2 and according manipulate the discharge flow of hydraulic fluid.
Referring to FIG. 1, the control valves 7 & 8 are in neutral position and hydraulic fluid supplied through the hydraulic fluid line 15 may be called as neutral channel.
The hydraulic fluid is pumped from hydraulic fluid reservoir 1 by the hydraulic pump unit 2 and supplied to the said hydraulic fluid line 15. The flow direction and channel of hydraulic fluid is highlighted by dark dotted lines as shown in FIG. 1.
The upstream pressure sensor 4 is placed between hydraulic pump unit 2 and the control valve 7 and it is mounted on the hydraulic fluid line 15 to measure upstream pressure across the hydraulic fluid line 15. When control valves are in neutral position (as shown in FIG.1), whole hydraulic fluid passed to the hydraulic reservoir 1 via orifice 13 and/or the relief valve 14. The downstream pressure sensor 12 is placed after the control valve 8 and it is mounted on the hydraulic fluid line 15 to measure downstream pressure across the hydraulic fluid line 15.
In the neutral position, whole hydraulic fluid gets transferred to reservoir through neutral channel or hydraulic fluid line 15. During this case, large amount of hydraulic fluid passes through the orifice 13 and/or relief valve 14. The downstream pressure sensor 12 observes high pressure across the hydraulic fluid line 15 due to high resistance of hydraulic fluid passing through the orifice 13. In such case, the downstream pressure sensor 12 sends output signals to the said ECU 3 in voltage, further signal to pump given in terms of PWM signal which further manipulate or control the discharge rate of the hydraulic fluid. In this case ECU 3 actually reduces the displacements of the hydraulic pump 2 which turns reduce the hydraulic fluid discharge rate.
The downstream pressure sensor 12 sends output signals in terms of PWM and frequency of the signals may be pre-determined. Hence real time pressure detection across the hydraulic fluid line 15 and real time control of the discharge rate of the hydraulic fluid through the hydraulic pump may be performed.
When above mentioned electrical system such as upstream sensor 4 or downstream sensor 12 get damaged or electrical system failed to communicate signals to ECU 3 then hydraulic pump 2 runs at full stroke and hydraulic fluid at the highest capacity starts flowing through the neutral channel 15. The orifice 21 & 22 are installed on the neutral line 15 which create hydraulic fluid pressure difference before and after the orifice 21 & 22. The compensator 23 is placed between hydraulic pressure line 16 & neutral line 15. The compensator 23 includes biasing member which maintains compensator 23 at original or normal position. Strength of biasing member is such that it can withhold pre-determined hydraulic fluid pressure. The compensator 23 is nothing but simple one way hydraulic valve along with biasing member.
As shown in FIG.1, the neutral channel 15 is open while hydraulic pressure line 16, 17, 18 & 19 are in closed. The compensator 23 is at original or initial position hence no hydraulic fluid passing through bypass path 19.
As illustrated in FIG.2, the modified hydraulic control system 200 for an earthmoving or construction machine to regulate and control a discharge flow of a variable displacement hydraulic pump when electronic system of such hydraulic control system get damaged or not working normally according to the first embodiment of the present invention is provided, the hydraulic pump runs at full stroke and hence hydraulic fluid at the highest capacity starts flowing through the neutral channel 15. The orifice 21 is placed on the neutral channel which creates hydraulic fluid pressure difference before and after the orifice 21. The compensator 23 along with biasing member installed in such way that it can withhold certain pre-determined hydraulic pressure across the hydraulic pressure line 23. The compensator 23 will start moving from its original position or normal position to other direction once hydraulic fluid pressure across the hydraulic pressure line 23 is more than pre-determined hydraulic pressure.
As shown in FIG.2, when hydraulic fluid pressure across the hydraulic pressure line 16 is more than pre-determined hydraulic pressure then compensator 23 starts pushing biasing member to other direction and thereafter bypasses path 19 gets open and excess hydraulic fluid starts flowing through bypass path 19 to reservoir 1 .
As illustrated in FIG.3, the modified hydraulic control system 200 for an earthmoving or construction machine to regulate and control a discharge flow of a variable displacement hydraulic pump according to the first embodiment of the present invention is provided, either of the control valves 7 & 8 start switching when spool in the control valves move in anyone direction. The hydraulic fluid is pumped from hydraulic fluid reservoir 1 by the hydraulic pump unit 2 and supplied to the said hydraulic fluid line 16. The flow direction and channel of hydraulic fluid is highlighted by dark dotted lines as shown in FIG. 3.
During this case, the hydraulic fluid lines deliver hydraulic fluid to main actuator/s to perform various functions such as digging, excavating, loading, hammering, compaction etc. In the FIG.3, the main actuator as hydraulic cylinder is in expanding position. The application of main actuator as hydraulic cylinder is merely shown as an example and application of actuator is not limited to thereto.
In such case, the neutral channel after orifice 21 gets closed and no hydraulic fluid flows from the neutral channel 15. The bypass path 19 also gets closed during such condition. When hydraulic pump 2 runs at full stroke the whole hydraulic fluid will pass through the hydraulic pressure line 16 to main actuator and compensator 23 will be at original or initial position.
As illustrated in FIG.4, the modified hydraulic control system 400 for an earthmoving or construction machine to regulate and control a discharge flow of a variable displacement hydraulic pump according to the first embodiment of the present invention is provided, either of the control valves 7 & 8 start switching in opposite direction when spool in the control valves move in other direction. The hydraulic fluid is pumped from hydraulic fluid reservoir 1 by the hydraulic pump unit 2 and supplied to the said hydraulic fluid line 17. The flow direction and channel of hydraulic fluid is highlighted by dark dotted lines as shown in FIG. 4.
During this case, the hydraulic fluid lines deliver hydraulic fluid to main actuator/s to perform various functions such as digging, excavating, loading, hammering, compaction etc. In the FIG.3, the main actuator as hydraulic cylinder is in retracting position. The application of main actuator as hydraulic cylinder is merely shown as an example and application of actuator is not limited to thereto.
In such case, the neutral channel after orifice 21 gets closed and no hydraulic fluid flows from the neutral channel 15. The bypass path 19 also gets closed during such condition. When hydraulic pump 2 runs at full stroke the whole hydraulic fluid will pass through the hydraulic pressure line 16 to main actuator and compensator 23 will be at original or initial position.
The output signals generated through upstream and downstream pressure sensors 4 & 12 transferred to the ECU 3. The output signal path is highlighted by thin dotted lines as shown in FIGS. 2, 3 & 4.
The continuous dark lines in all FIGS.2, 3 & 4 represent that those lines are filled with hydraulic fluid and there is no movement of hydraulic fluid across the lines.
The relief valves 6 & 14 are fixed in the system to protect the system from the excess pressure and thermal expansion. The hydraulic pressure across the hydraulic pressure line 15 get increased due to excessive pressure then the relief valve 14 get opened and hydraulic fluid delivered to reservoir 1 via relief valve 14. The second relief valve 6 is installed on the hydraulic fluid line 18 which protect the hydraulic pump and hydraulic system from excessive pressure. Whenever hydraulic system observe any abnormality due to the hydraulic pump and/or actuator stalling or overloading then to protect the hydraulic system, the relief valve 6 get opened and hydraulic fluid delivered to reservoir 1 via relief valve 6.
This kind of hydraulic schematic gives significant energy saving in the system without affecting much on the performance. The energy saved by using above explained system can be used in other hydraulic power requirements. If saved energy is not used in other hydraulic power requirement then also it may help in reducing the energy load on the hydraulic pump.

Claims:

1. A modified hydraulic control system to control discharge flow of a variable displacement pump in an earthmoving or construction equipment comprising:
? at least one hydraulic fluid reservoir through which hydraulic fluid may be circulated to a hydraulic fluid line;
? at least one hydraulic fluid line to circulate the hydraulic fluid;
? at least one variable displacement pump for pumping the hydraulic fluid from the hydraulic reservoir and supply it to the hydraulic fluid line ;
? at least one hydraulic fluid pressure relief valve and control valve for controlling fluid circulation across the hydraulic fluid line;
? at least one upstream hydraulic fluid pressure sensing unit mounted on hydraulic fluid line and placed between the variable displacement pump and the control valve;
? at least one downstream hydraulic fluid pressure sensing unit mounted on hydraulic fluid line and placed after the control valve;
? at least one compensator for bypass excess hydraulic fluid to the reservoir via bypass path;
? at least one orifice unit and at least one check valve mounted on the hydraulic fluid line; and
? at least one electronic control unit for processing input data received through said the hydraulic fluid sensing unit and for control functioning of the variable displacement pump.
2. The modified hydraulic control system to control discharge flow of a variable displacement pump claimed in claim 1, wherein the variable displacement pump for pumping hydraulic fluid from the hydraulic reservoir driven by either machine engine, external engine, battery, external or internal power source, combination of thereof or any other means.
3. The modified hydraulic control system to control discharge flow of a variable displacement pump claimed in claim 1, wherein the orifice is installed on the neutral channel for creating hydraulic fluid pressure difference before and after the orifice on the neutral channel.
4. The modified hydraulic control system to control discharge flow of a variable displacement pump claimed in claim 1, wherein the compensator includes one way to two way control valve and at least one biasing member.
5. The modified hydraulic control system to control discharge flow of a variable displacement pump claimed in claim 1, wherein one end of compensator is installed on the hydraulic pressure line 16 while other end is installed on neutral channel 15.
6. The modified hydraulic control system to control discharge flow of a variable displacement pump claimed in claim 1, wherein strength of material of biasing member is such that it maintains the compensator at original or initial position.
7. The modified hydraulic control system to control discharge flow of a variable displacement pump claimed in claim 1, wherein strength of material of biasing member is such that it withhold pre-determined hydraulic fluid pressure.
8. The modified hydraulic control system to control discharge flow of a variable displacement pump claimed in claim 1, wherein hydraulic pressure generated before the orifice 21 is more than the pre-determined hydraulic pressure then the compensator start pushing biasing member to other direction and thereafter hydraulic fluid passes to reservoir via the bypass path 19.
9. The modified hydraulic control system to control discharge flow of a variable displacement pump claimed in claim 1, wherein compensator may be includes hydraulic pressure sensing unit for measuring hydraulic fluid pressure across the hydraulic pressure line 16 and neutral channel 15.
10. The modified hydraulic control system to control discharge flow of a variable displacement pump claimed in claim 1, wherein the variable displacement pump runs at full stroke when electrical system gets damage or fail to communicate signals to the electronic control unit.
11. The modified hydraulic control system to control discharge flow of a variable displacement pump claimed in claim 1, wherein the control valves are controlled either mechanically, hydraulically , electrically or combination of thereof.