Hydraulic hybrid system for rotatory applications

Abstract

A hydraulic hybrid system for rotatory applications has an actuator (49, 91) in the form of a motor pump unit (91). The motor pump unit is coupled to a rotatory-operating device (94) and works as a consumer of hydraulic energy in one operating state of the device (94) and works as a producer of hydraulic energy in another operating state of the device (94). A hydraulic accumulator (1) can be charged by the motor pump unit (91) for energy storage in the one operating state and can be discharged for energy release to the motor pump unit (91) in the other operating state. The hydraulic accumulator is an adjustable hydropneumatic piston accumulator (1) in which a plurality of pressure chambers (19, 21, 23, 25) are delimited by active surfaces (11, 13, 15, 17) of different sizes on the fluid side of the accumulator piston (5). An adjusting arrangement (51) connects a selected pressure chamber (19, 21, 13, 25) or a plurality of selected pressure chambers (19, 21, 23, 25) of the piston accumulator (1) to the actuator (49, 91) depending on the prevailing pressure level on the gas side of the piston accumulator (1) and at the actuator (49, 91).

Claims

1. A hydraulic hybrid system for rotary applications, comprising: a motor pump unit; a rotary-operating device being coupled to said motor pump unit, being a consumer of hydraulic energy in a first operating state and being a producer of hydraulic energy in a second operating state; an adjustable hydropneumatic piston accumulator being connected in fluid communication with said motor pump unit, being chargeable by said motor pump unit for energy storage in the second operating state and being discharged for energy release to said motor pump unit in the first operating state, said piston accumulator having a plurality of separate pressure chambers adjacent to active surfaces of different sizes on a fluid side of an accumulator piston in said piston accumulator, said piston accumulator having a gas side and having two of said active surfaces inside said accumulator piston in a stepped configuration; and an adjustment assembly connecting a selected one of said pressure chambers or a plurality of selected ones of said pressure chambers of said piston accumulator to said motor pump unit depending on prevailing pressure levels on said piston accumulator, and motor pump unit and said rotary-operating device.

2. A hydraulic hybrid system according to claim 1 wherein said rotary-operating device is a traction device.

3. A hydraulic hybrid system according to claim 1 wherein said piston accumulator comprises an accumulator housing having mating surfaces corresponding to and adjacent to said active surfaces of said accumulator piston, said mating surfaces of said accumulator housing and said active surfaces associated therewith delimit said separate fluid pressure chambers.

4. A hydraulic hybrid system according to claim 3 wherein said mating surfaces on said accumulator housing are disposed in steps axially spaced from one another.

5. A hydraulic hybrid system according to claim 4 wherein said active surfaces of different sizes and said mating surfaces on said accumulator housing are annular and concentric to a longitudinal axis of said piston accumulator.

6. A hybrid system according to claim 5 wherein said mating surfaces on said accumulator housing are on a housing projection extending inside said piston accumulator.

7. A hybrid system according to claim 3 wherein said mating surfaces on said accumulator housing are on a housing projection extending inside said piston accumulator.

8. A hydraulic hybrid system according to claim 1 wherein said adjustment assembly comprises selector valves selectively connecting the selected one or the selected ones of said pressure chambers for charging and discharging to said motor pump unit and connecting remaining ones of said fluid pressure chambers to a tank.

9. A hydraulic hybrid system according to claim 1 wherein a control logic unit is connected to a speed sensor connected to said motor pump unit and generating signals of a rotational speed of said motor pump unit used by said control logic unit.

10. A hydraulic hybrid system according to claim 1 wherein said adjustment assembly comprises directional valves controlling a connection between said pressure chambers of said accumulator and said motor pump unit.

11. An adjustable hydropneumatic piston accumulator, comprising: an accumulator housing having an internal chamber, said internal chamber having a plurality of active housing surfaces of different sizes and having a longitudinal axis; an accumulator piston axially movable in said accumulator housing along said longitudinal axis and separating said internal chamber of said accumulator housing into a fluid side and a gas side, said accumulator piston having two active piston surfaces of different sizes inside said accumulator piston in a stepped configuration; and a plurality of separate pressure chambers adjacent to said housing surfaces and said piston surfaces in said fluid side.

12. An adjustable hydropneumatic piston accumulator according to claim 11 wherein said housing surfaces and said piston surfaces delimit said pressure chambers in directions along said longitudinal axis.

13. An adjustable hydropneumatic piston accumulator according to claim 12 wherein said housing surfaces are disposed in steps axially spaced from one another.

14. An adjustable hydropneumatic piston accumulator according to claim 13 wherein said piston surfaces and said housing surfaces are annular and concentric to said longitudinal axis.

15. An adjustable hydropneumatic piston accumulator according to claim 14 wherein said housing surfaces are on a housing projection extending inside said accumulator piston.

16. An adjustable hydropneumatic piston accumulator according to claim 11 wherein said housing surfaces are on a housing projection extending inside said accumulator piston.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Referring to the drawings that form a part of this disclosure:

(2) FIG. 1 is a highly schematic, simplified side view in section of a hydropneumatic piston accumulator in a multi-stage design for use in the system according to an exemplary embodiment of the invention;

(3) FIG. 2 is a schematic diagram of the piston accumulator of FIG. 1 in conjunction with associated system components of the system according to the exemplary embodiment of the invention; and

(4) FIG. 3 is the piston accumulator of FIG. 1 in a hydraulic circuit diagram of a hybrid system according to the exemplary embodiment of the invention depicted by schematic symbols.

DETAILED DESCRIPTION OF THE INVENTION

(5) The hydropneumatic piston accumulator 1, which is shown in a schematic, simplified depiction in FIG. 1, has an accumulator piston 5 that is axially movably guided in an accumulator housing 3. The accumulator piston separates a gas side 7, on which a filling port 9 is located, from fluid-side pressure chambers in the accumulator housing 3. The accumulator piston 5 is designed in the manner of a step piston such that, in combination with corresponding stepped portions of the accumulator housing 3, the accumulator piston delimits fluid-side pressure chambers 19, 21, 23 and 25, which are adjacent to active surfaces of different sizes on the fluid side of the accumulator piston 5. In FIG. 1, these active surfaces 11, 13, 15 and 17 are arranged from the largest surface to the smallest surface. The active surfaces 11, 13 and 15 are each formed by annular surfaces disposed concentrically relative to the longitudinal axis, which surfaces surround the inner-most active surface 17 in the form of a circular surface. Pressure chambers 19, 21 or 23, respectively, which are adjacent to the active surfaces 11, 13 and 15, are delimited by mating surfaces 27 or 29 or 31, respectively, of the accumulator housing 3, as well as by cylinder surfaces 35 of the cylinder housing 3 and cylinder surfaces 37 on the accumulator piston 5. The pressure chamber 25 adjacent to the active surfaces 17 is delimited by a mating surface 33 of the accumulator housing 3 as well as a cylinder surface 39 of the accumulator piston 5.

(6) A fluid port 41, 43, 45 or 47, respectively, is provided for each pressure chamber 19, 21, 23, 25. Just as the active surfaces 11, 13, 15 and 17 are disposed on the accumulator piston 5, the associated mating surfaces 27, 29, 31 or 33 respectively are disposed on the accumulator housing 3 in steps that are axially spaced relative to one another.

(7) FIG. 2 shows the piston accumulator 1 in conjunction with associated system components. An actuator 49 is operatively connected to an adjustment assembly 51. The actuator 49 has a motor pump unit 91 (FIG. 3) coupled with a device 94 (FIG. 3). A control logic unit 53 is associated with the adjustment assembly 51, which logic unit actuates a valve arrangement 57 of the adjustment assembly 51 by a control and regulation unit 55. As will be explained in greater detail on the basis of FIG. 3, the valve arrangement 57 has selector valve, which produces selected fluid connections between the actuator 49 and the fluid ports 41, 43, 45, 47 of the piston accumulator 1, to selectively activate the pressure chambers 19, 21, 23 and 25 for charging and discharging processes. To this end, the control logic unit 53 processes signals, which are provided by sensor devices and which represent or provide signals representative of the operating states of actuator 49 and piston accumulator 1. Only one of the sensor devices, a pressure sensor 59 at the filling port 9 of the piston accumulator 1, is shown in FIG. 2.

(8) FIG. 3 shows the hydraulic circuit diagram of an embodiment of the hydraulic hybrid system, according to an exemplary embodiment of the invention, wherein the actuator 49 has a motor pump unit 91. The pump shaft 92 of motor unit 91 is coupled to a drive source on one side, for example an internal combustion engine 93, and is coupled to a rotary driven device 94 on the other side. This device 94 may be working hydraulics, a traction drive or the like, i.e. it may be a device, which works as a consumer of hydraulic energy in one operating state, and as a producer of hydraulic energy in other operating states, for example in the case of braking processes of the traction drive. A corresponding torque is generated at the pump shaft 92. The pressure side of the motor pump unit 91 is connected, by a check valve 95, to a main line 71 of the adjustment assembly 91 that guides the system pressure. These adjustment assemblies each have a connection line 73, 75, 77, 80, respectively, which connection lines serve as a connection between the main line 71 and each of the fluid ports 41, 43, 45 and 47 of the piston accumulator 1. A valve group, which can be actuated by the control logic unit 53, is located in each of the connecting lines, which valve groups are symbolically designated as v.sub.1, v.sub.2, etc. Each valve group is formed by two fast switching 2/2-way-valves 79 and 81, and are identified with indices 1 to 4 for the valve groups v.sub.1 to v.sub.4. Each of the connecting lines 73, 75, 77, 80 can be connected or blocked from the associated fluid ports 41, 43, 45 or 47 respectively of the piston accumulator 1 by the directional valves 81.1 to 81.4. The respective connecting lines can be connected to the tank 83 by the directional valves 79.1 to 79.4.

(9) A pressure sensor 59 that detects the gas side pressure is provided at the filling port 9 of the piston accumulator 1. A pressure sensor 63 that detects the system pressure is provided at the main line 71. A speed sensor 96 is provided at the drive motor 93. Each sensor generates the signals that are to be processed by the control logic unit 53. The control logic unit 53 decides, on the basis of these signals, which of the connecting lines 73, 75, 77 or 80, or which combination of these connecting lines, will establish the connection between the main line 71 and the respective associated fluid ports 41, 43, 45, 47 on the piston accumulator 1. The selection is thereby made as to which of the pressure chambers 19, 21, 23, 25, or which combination of these pressure chambers, is most suited for a charging process or discharging process with the respective prevailing pressure level of the system pressure (main line 71) and of the accumulator 1. In the case of discharging processes, the recovered energy is returned by a selector valve 97 to the suction side of the motor pump unit 91 from the main line 71, which main line is secured by means of a pressure relief valve 86. For charging processes, the selector valve 97 is closed, and one connecting line or a plurality of the connecting lines 73, 75, 77, 80 are activated by the directional valves 81.1 to 81.4. The respective associated directional valves 79.1 to 79.4 are closed. On the other hand, the directional valves 79.1 to 79.4 form the connection to the tank 83 for the respective non-activated connecting lines 73, 75, 77, 80, so that the connected, non-selected pressure chambers 19, 21, 23 or 25 of the accumulator 1 can be refilled without pressure in the case of discharging processes, and can be refilled from the tank 83 in the case of charging processes. In the case of changing system conditions, the respective selected combination of the active surfaces 11, 13, 15, 17 can be changed during the charging processes or discharging processes. An inverse shuttle valve 99 is provided to discharge the excess amount of fluid in the circuit coming from the accumulator 1 during the discharging processes, from the now unpressurized downstream side of the motor pump unit 91 to the tank 83. The upstream side of the motor pump unit 91 can be connected to the tank 83 by this shuttle valve for the refilling operations during charging processes. The motor pump unit 91 has a fixed displacement pump.

(10) While one embodiment has been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the claims.