HYDRAULIC ACCUMULATOR SYSTEM

TECHNICAL AREA

The invention relates to an hydraulic accumulator system for storing and producing energy.

BACKGROUND

A typical accumulator is a unit used to store and supply energy. Among the different types of accumulators available, electrical and hydraulic accumulators are most commonly used. Examples of electrical accumulators include batteries and capacitors. Further, examples of hydraulic accumulators are hydraulic systems, such as hydraulic cylinders used in the drive system of hydraulic machinery, which can store a hydraulic fluid under pressure. The Hydraulic accumulators are usually used for power cranes and operate bascule/draw bridges.

The working of the various types of accumulators is described below with the help of examples. For instance, in case of a hybrid car, a dual energy source is provided to drive the transmission system of the car. The dual energy source includes an IC engine and a battery pack (electrical accumulator). In a scenario, when the car is decelerating or navigating a down hill slope, the car consumes a lesser amount of energy and gathers momentum due to inertia. Accordingly, the surplus energy available from the IC engine is converted and is supplied to the integrated battery pack for storage. In another scenario, when the car is being driven on a flat highway, the electrical energy stored in the battery pack is supplied to the transmission system of the car. It will be apparent that in this scenario maximum energy is derived from the battery pack. This energy storage and supply to/from the system is a regenerative process and helps to save fuel and conserves energy. However, there are several limitations to the use of batteries in the exemplary system described above such as low efficiency, high energy losses, high purchasing cost and frequent maintenance. Further, storing electrical energy by charging the batteries takes a considerable amount of time. Similarly, the hydraulic accumulator can also be connected to various systems as described above. To further elaborate with the help of an example, the hydraulic accumulator is connected to a public electrical grid to store and supply electrical energy. Such arrangements are generally used in areas where there is an intermittent supply of electrical energy. In such scenarios, the hydraulic accumulator stores electrical energy whenever surplus electrical energy is available from the supply grid. This availability might be due to off peak hours in a day. Further, the hydraulic accumulator provides electrical energy to the grid when there is an extra demand on the public supply grid for more electrical energy.

Though hydraulic accumulators are used in the above mentioned arrangement to store and supply energy, the arrangement is totally standalone. Further, the arrangement stores/provides energy to/from the public electric grid alone. Thus, there is a need to properly integrate the hydraulic accumulator with numerous existing systems, such as a battery, where the supply, storage and usage of energy among systems are performed in a regenerative manner.

In light of the above discussion, there exists a room in the art for further improvement and development of an integrated system that is cost effective and obviates the limitations of the existing systems.

SUMMARY OF THE INVENTION

It is an object of the invention to provide an integrated electro-hydraulic hybrid system for storing and producing energy by using a hydraulic accumulator, a hydraulic pump/motor and an electric motor/ generator. According to the present invention an integrated electro-hydraulic hybrid system to store and produce energy is provided. The integrated electro- hydraulic hybrid system comprises a hydraulic accumulator, a hydraulic pump/motor operatively coupled with the hydraulic accumulator, an electric motor/generator directly coupled with the hydraulic pump/motor, the electric motor/generator interacting with the hydraulic pump/motor to load the hydraulic accumulator, and one or more peripheral units, the one or more peripheral units being at least one of a hydraulic system and an electrical system, wherein the electric motor/generator is coupled with at least one electrical system to receive/supply electrical energy and the hydraulic accumulator is coupled with at least one hydraulic system to receive/supply hydraulic energy.

According to one aspect of the invention the hydraulic accumulator receives the energy from the at least one electrical system, the energy being transferred from the at least one electrical system to the hydraulic accumulator in interaction with the electric motor/generator and the hydraulic pump/motor. In a further aspect of the invention the hydraulic accumulator receives the energy from the at least one hydraulic system.

According to another aspect of the invention the hydraulic accumulator releases the stored energy directly to the at least one coupled hydraulic system. Alternatively, the hydraulic accumulator releases the stored energy to the at least one electrical system, the energy being transferred by the hydraulic accumulator in interaction with the hydraulic pump/motor and the electric motor/generator. A further possibility is that the hydraulic accumulator is loaded in parallel by the energy supplied by the at least one electrical system and the at least one hydraulic system. The integrated electro-hydraulic hybrid system further preferably comprises a reservoir including a fluid.

According to yet another aspect the integrated electro-hydraulic hybrid system further comprises a valve block operatively coupled to the hydraulic accumulator, the valve block configured to control the loading of the fluid into the hydraulic accumulator.

The integrated electro-hydraulic hybrid system comprises according to one aspect of the invention a pressure relief valve, the pressure relief valve functionally coupled to the hydraulic accumulator, the pressure relief valve configured to discharge the extra energy generated by the hydraulic accumulator. According to yet a further aspect of the invention the system is mobile.

The invention describes an integrated electro-hydraulic hybrid system to store and produce energy. The integrated electro-hydraulic hybrid system includes a hydraulic accumulator, a hydraulic pump/motor operatively coupled with the hydraulic accumulator, an electric motor/generator directly coupled with the hydraulic pump/motor, and one or more peripheral units. The one or more peripheral units may either be a hydraulic system or an electrical system. Further, the electric motor/generator is coupled with at least one electrical peripheral unit to receive/supply electrical energy, wherein the electric motor/generator interacts with the hydraulic pump/motor to load the hydraulic accumulator. Similarly, in an embodiment of the invention, the hydraulic accumulator is directly coupled with at least one hydraulic peripheral unit to receive/supply hydraulic energy. It is an advantage of the invention that the integrated electro-hydraulic hybrid system supplies and receives energy from both the electric and hydraulic peripheral units. It is further an advantage of the invention that the integrated electro-hydraulic hybrid system can be charged faster than the systems including the conventional electrical accumulators. Moreover, the integrated electro- hydraulic hybrid system can be charged in parallel by the electric, as well as hydraulic, peripheral units. This rapid charging ability significantly reduces the time required to bring the electro-hydraulic hybrid system to a ready state. It is an advantage of the invention that the integrated electro-hydraulic hybrid system has lesser energy losses as compared with the conventional electric accumulators. Furthermore, the integrated electro-hydraulic hybrid system requires less maintenance and is, therefore, cost effective.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following section, the invention will be described in a greater detail with reference to embodiments shown by the enclosed figure. It should be emphasised that the embodiment shown is used for example purposes only and should not be used to limit the scope of the invention.

The invention and embodiments thereof will now be further elucidated by means of a figure.

Figure 1 illustrates an integrated electro-hydraulic hybrid system in accordance with an embodiment of the invention. A person skilled in the art will readily appreciate that various features disclosed in the description may be modified, and that various embodiments disclosed and/or claimed may be combined without departing from the scope of the invention. DISCLOSURE OF PREFERRED EMBODIMENTS

Figure 1 illustrates an integrated electro-hydraulic hybrid system 100, in accordance with an embodiment of the invention. The integrated electro- hydraulic hybrid system 100 includes a hydraulic accumulator 102, an electric motor/generator 106, a conduit 1 10, and a hydraulic pump/motor 1 12. Further, the integrated electro-hydraulic hybrid system 100 includes one or more peripheral units 120, such as a peripheral unit 120a, a peripheral unit 120b, a peripheral unit 120c, a peripheral unit 120d, and a peripheral unit 120e. The integrated electro-hydraulic hybrid system 100 also includes a fluid reservoir 1 18, a pressure relief valve 1 14, a valve block 1 16, an inverter 108, and a connection means 104. The hydraulic accumulator 102 interacts with the peripheral units 120 to store the energy received from the peripheral units 120. Further, the hydraulic accumulator 102 also interacts with the peripheral units 120 to supply energy to the peripheral units 120. The working of the integrated electro-hydraulic hybrid system 100 to store and produce energy is described in detail below. In a preferred embodiment of this invention, the electric motor/generator 106 is connected to the hydraulic pump/motor 1 12. The hydraulic pump/motor 1 12 is further connected to the hydraulic accumulator 102 and to the fluid reservoir 1 18 by means of the conduit 1 10. Furthermore, the electric motor/generator 106 is connected to one or more of the peripheral units 120. In an embodiment of the invention, the peripheral units 120 connected to the electric motor/generator 106 are an electrical system, such as the peripheral unit 120b, the peripheral unit 120c, the peripheral unit 120d, and the peripheral unit 120e. Examples of electrical peripheral units 120 include, but are not limited to, a battery, an electric hydraulic system, and a transmission system. In another embodiment of the invention, the peripheral unit 120 is a hydraulic system, such as the peripheral unit 120a, and is directly connected to the hydraulic accumulator 102. An example of hydraulic peripheral units is the hydraulic system of a mobile equipment such as a reach stacker. In operation, when the peripheral units 120 are an electrical system, the peripheral units 120 b-e supplies/receives electrical energy to/from the electric motor/generator 106. In an embodiment, when the peripheral units 120 b-e supplies electrical energy to the electric motor/generator 106, the electric motor/generator 106 drives the hydraulic pump/motor 1 12. Herein, the electric motor/generator 106 acts as a motor and the hydraulic pump/motor 1 12 acts as a pump. Accordingly, the hydraulic pump 1 12 pumps the fluid under pressure from the fluid reservoir 1 18 and loads the hydraulic accumulator 102. In other words, the electrical energy supplied by the electrical peripheral units 120 b-e is converted and stored as hydraulic energy in the hydraulic accumulator 102. In other embodiment of the invention, the energy stored in the hydraulic accumulator 102 is supplied to the electrical peripheral units 120 b-e as required. In this case, the hydraulic accumulator 102 releases the stored pressurized fluid which drives the hydraulic pump/motor 1 12. Herein, the hydraulic pump/motor 1 12 acts as motor and the electric motor/generator 106 acts as a generator. Accordingly, the armature (not shown) of the hydraulic motor 1 12 rotates under the action of the pressurized fluid and drives the electric generator 106 to produce electrical energy. The electrical energy thus produced is provided to one or more of the electrical peripheral units 120 b-e as required. In an embodiment of the invention, the inverter 108 is connected to the electric motor/generator 106. The inverter 108 is used to store the electric energy produced by the electric generator 106. The stored electrical energy can be later transferred to the at least one electrical peripheral unit 120 b-e of the peripheral units 120. Similarly, when the peripheral units 120 is a hydraulic system, the peripheral units 120a is directly connected to the hydraulic accumulator 102 through the valve block 1 16 and the connection means 104. In an embodiment, hydraulic energy in the form of pressurized fluid available from the peripheral unit 120a is directly used to load the hydraulic accumulator 102. The valve block 1 16 is used to regulate the loading of the hydraulic accumulator 102. It should be appreciated that the valve block 1 16 can be any suitable valve assembly. In another embodiment, if the peripheral unit 120a requires hydraulic energy, the hydraulic energy stored in the hydraulic accumulator 102 is directly given to the peripheral unit 120a. The hydraulic energy supplied to the peripheral unit 120a is regulated by the valve block 1 16. In an embodiment of the invention, the hydraulic accumulator 102 is loaded in a parallel arrangement by one of the peripheral units120 b-e supplying electrical energy, and the peripheral unit 120a supplying hydraulic energy. Further, the hydraulic accumulator 102 is able to supply in a parallel manner the hydraulic energy to the peripheral unit 120a and one of the peripheral units 120 b-e. The hydraulic energy supplied to the peripheral units 120 b-e through the hydraulic pump/motor 1 12 and the electric motor/generator 106 is in electrical energy form.

In an embodiment of the invention, the hydraulic accumulator 102 is connected with the pressure relief valve 1 14. The pressure relief valve 1 14 is configured to release the additional pressure in the hydraulic accumulator 102 when the pressure exceeds a desired value. In other words, the pressure relief valve 1 14 is activated when the pressure inside the hydraulic accumulator 102 exceeds a threshold predefined value. In an embodiment of the invention, the pressure that is discharged by operating the pressure relief valve 1 14 is used for various purposes, such as providing brake power to an automotive vehicle.

In an embodiment of the invention, the pressure relief valve 1 14 can also be replaced by/configured as an electric resistance unit. The electric resistance unit is configured to operate when the pressure in the hydraulic accumulator 102 exceeds a desired value. In other words, the electric resistance unit is activated when the pressure inside the hydraulic accumulator 102 exceeds a threshold predefined value. Thus, when the hydraulic accumulator 102 is completely loaded, the electric motor/generator 106 driving the hydraulic pump/motor 1 12 to load the hydraulic accumulator 102 is stopped and the excess electric energy available from the one or more of the peripheral units 120 b-e is dissipated as heat through the electric resistance.

The working of the integrated electro-hydraulic system 100 with the peripheral units 120 will be described in detail below.

In an exemplary embodiment of the invention, the peripheral unit 120b is a battery pack. The battery pack is connected to the electric motor/generator 106. Further, the battery pack receives/supplies electrical energy from/to the electric motor/generator 106. In operation, when electrical energy is received from the battery pack, the electric motor/generator 106 operates the hydraulic pump/motor 1 12 to load the hydraulic accumulator 102. Thus, the hydraulic accumulator 102 is loaded with the fluid drawn from the fluid reservoir 1 18 in a pressurized manner. Further, when the battery pack requires electrical energy for charging, the pressurized fluid stored in the hydraulic accumulator 102 is released. The released pressurized fluid operates the hydraulic pump/motor 1 12 and the electric motor/generator 106 to generate electrical energy. The electrical energy thus generated is provided to the battery pack for charging.

In another exemplary embodiment of the invention, the peripheral unit 120c is an electrically driven hydraulic system. The electrically driven hydraulic system is connected to the electric motor/generator 106. Further, the electrically driven hydraulic system receives/supplies electrical energy from/to the electric motor/generator 106. The hydraulic system of the electrically driven hydraulic system may be the hydraulic system of a mobile equipment such as a reach stacker or any other automotive vehicle.

Generally, the reach stacker is used to lower and raise loads such as containers or pallets in a cargo handling area. Further, the reach stacker requires hydraulic energy to raise loads and releases hydraulic energy when load is lowered, or the reach stacker retracts back to a neutral position. In operation, when the reach stacker requires hydraulic energy to raise a load, the pressurized fluid stored in the hydraulic accumulator 102 is released. The pressurized fluid released operates the hydraulic pump/motor 1 12 and the electric motor/generator 106 to generate electrical energy. Thereafter, the electrical energy generated is provided to the reach stacker for raising the load. Further, hydraulic energy is released when the load is lowered or the reach stacker retracts back to a neutral position. The released hydraulic energy is converted into electrical energy by the reach stacker and is provided to the electric motor/generator 106. The electric motor/generatorl 06 operates the hydraulic pump/motor 1 12 to load the hydraulic accumulator 102. Thus, the hydraulic accumulator 102 is loaded in a pressurized manner by drawing the fluid from the fluid reservoir 1 18.

In yet another exemplary embodiment of the invention, the peripheral unit 120d is a transmission system. The transmission system is connected to the electric motor/generator 106. Further, the transmission system can receive/supply electrical energy to the electric motor/generator 106.

In an embodiment of the invention, the transmission system is a transmission system of the mobile equipment such as a reach stacker or any other automotive vehicle. It will be apparent to anybody skilled in the art that the transmission system is used to transmit power generated by the IC engine of the mobile equipment to the wheels of the mobile equipment. The power transmission is conducted through a drive shaft and an axle arrangement. In operation, when the mobile equipment is decelerating or navigating a downhill slope, the energy produced by the IC engine of the mobile equipment is used to a lesser extent. The extra energy available is converted to electrical energy by the mobile equipment. Further, this electrical energy is provided to the electric motor/generator 106. The electric motor/generator 106 operates the hydraulic pump/motor 1 12 to load the hydraulic accumulator 102. Thus, the hydraulic accumulator 102 is loaded with the fluid drawn from the fluid reservoir 1 18 in a pressurized manner. Further, when, the transmission system needs power, the pressurized fluid stored in the hydraulic accumulator 102 is released. The pressurized fluid released operates the hydraulic pump/motor 1 12 and the electric motor/generator 106 to generate electrical energy. The electrical energy thus generated is provided to the transmission system by the electric motor/generator 106.

As mentioned above, the extra pressure generated in the hydraulic accumulator 102 is put to various uses, such as providing brake power to an automotive vehicle. To elaborate with the help of an example, when an automotive vehicle is navigating a downhill slope, constant brake power is needed to guide the vehicle smoothly. Further, during this period, extra energy is available from the automotive vehicle and is stored in the hydraulic accumulator 102. Thus, above a certain pre-defined threshold point, when the hydraulic accumulator 102 is fully loaded with the energy available, the extra incoming energy is dissipated via the pressure relief valve 1 14. The pressure relief valve 1 14 is operatively coupled with the vehicle brake system (part of the transmission system) to supply adequate brake power. In an exemplary embodiment of the invention, the peripheral unit 120d is a generator driven by an IC engine. The generator driven by the IC engine is connected to the electric motor/generator 106. Further, the generator driven by the IC engine can receive/supply electrical energy to the electric motor/generator 106. Generally, the IC engine is the IC engine of a mobile equipment such as a reach stacker or any other automotive vehicle. In operation, when the demand of energy is less on the mobile equipment, the extra energy generated by the IC engine is used to run the generator to produce electrical energy. The electrical energy generated is provided to the electric motor/generator 106. The electric motor/generatorl 06 operates the hydraulic pump/motor 1 12 to load the hydraulic accumulator 102. Thus, the hydraulic accumulator 102 is loaded with the fluid drawn from the fluid reservoir 1 18 in a pressurized manner. Further, when the mobile equipment needs energy, the pressurized fluid stored in the hydraulic accumulator 102 is released. The pressurized fluid released operates the hydraulic pump/motor 1 12 and the electric motor/generator 106 to produce electrical energy. The electrical energy thus generated is provided to the mobile equipment by the electric motor/generator 106.

In an exemplary embodiment of the invention, the peripheral unit 120a is a hydraulic system. The hydraulic system is connected to the hydraulic accumulator 102. Further, the hydraulic system receives/supplies hydraulic energy to the hydraulic system 102. The hydraulic system may be the hydraulic system of a mobile equipment such as a reach stacker or any other automotive vehicle. Generally, the reach stacker is used to lower and raise loads such as containers or pallets in a cargo handling area. Further, the reach stacker requires hydraulic energy to raise loads and expels hydraulic energy when load is lowered or the reach stacker retracts back to a neutral position.

In operation, when energy is needed by the reach stacker to raise a load, pressurized fluid is directly supplied to the hydraulic system of the reach stacker by the hydraulic accumulator 102. Further, when load is lowered by the reach stacker pressurized fluid is released. The pressurized fluid released is directly supplied to the hydraulic accumulator 102 for loading and storing.

As discussed earlier, the supply and release of the pressurized fluid is controlled and regulated. The controlled release and supply of the pressurized fluid at both the ends is performed by regulating a corresponding valve block. Thus, it will be apparent to anybody skilled in the art that the hydraulic pump/motor 1 12 and the electric motor/generator 106 assembly is bypassed and pressurized fluid is directly transferred between the hydraulic system of the reach stacker and the hydraulic accumulatorl 02. The integrated electro-hydraulic hybrid system described above has a number of advantages. The integrated electro-hydraulic hybrid system supplies and receives energy from both electric and hydraulic energy based peripheral units. The integrated electro-hydraulic hybrid system is charged faster than the systems including the conventional electric accumulators. Moreover, the integrated electro-hydraulic hybrid system is charged in parallel by the electric peripheral units as well as hydraulic peripheral units. This rapid charging ability significantly reduces the time needed to bring the electro-hydraulic hybrid system to a ready state. Thus, the integrated electro- hydraulic hybrid system is able to receive/supply energy in a lesser time than the systems, including the conventional electric accumulators. Further, the integrated electro-hydraulic hybrid system has very lower energy losses than the systems including the conventional electric accumulators. Furthermore, the integrated electro-hydraulic hybrid system requires less maintenance and is, therefore, more cost effective. Also, when the integrated electro-hydraulic hybrid system is connected with the transmission system of mobile equipment, energy supply, storage and usage is performed in a regenerative manner. This arrangement helps to reduce the use of precious nonrenewable sources of energy as less fuel is consumed and thus helps in conserving energy.