Hydraulic system with an energy recovery circuit

Abstract

Hydraulic systems and methods comprising a source of hydraulic pressure; a hydraulic load; and an energy recovery circuit. The source of hydraulic pressure is fluidly connected to the hydraulic load through a first hydraulic channel with an orifice. The energy recovery circuit includes a recovery channel which is fluidly connected at its first end to the orifice on the side of it which is connected to the source of hydraulic pressure, and which is fluidly connected at its second end to a hydraulic motor.

Claims

1. A hydraulic system, comprising: a source of hydraulic pressure; a hydraulic load; an energy recovery circuit, wherein the source of hydraulic pressure is fluidly connected to the hydraulic load through a first hydraulic channel including an orifice, wherein the energy recovery circuit includes a recovery channel which is fluidly connected at its first end to the orifice on the side of the orifice which is connected to the source of hydraulic pressure, and which is fluidly connected at its second end to a hydraulic motor, wherein the hydraulic motor is mechanically coupled to an electric generator; and a controller which is configured to control a hydraulic resistance of the recovery circuit based on the value of the hydraulic flow to the hydraulic load and/or a hydraulic pressure at the hydraulic load or on a pressure drop across the orifice, the controller controlling a position of a steering element depending on a comparison of pressures in a first steering chamber selectively fluidly connected to the recovery channel and a second steering chamber continuously fluidly connected with the recovery channel.

2. The hydraulic system according to claim 1, wherein the controller is connected to one or more hydraulic sensors wherein at least a first hydraulic sensor is located in the first hydraulic channel between the orifice and the hydraulic load or at the hydraulic load, wherein the first hydraulic sensor is configured to be a pressure sensor and/or a flow sensor.

3. The hydraulic system according to claim 2, wherein the controller is connected to a second hydraulic sensor wherein the second hydraulic sensor is located in the first hydraulic channel between the orifice and the source of hydraulic pressure or at the source of hydraulic pressure, wherein the second hydraulic sensor is configured to be a pressure sensor and/or a flow sensor.

4. The hydraulic system according to claim 3, wherein the controller is connected to one or more hydraulic sensors through an electric or a hydraulic connection.

5. The hydraulic system according to claim 1, wherein the hydraulic motor is configured such that its hydraulic resistance is controlled by the controller.

6. The hydraulic system according to claim 1, wherein the electric generator is configured such that its mechanical resistance is controlled by the controller.

7. The hydraulic system according to claim 6, wherein an electrical converter which is electrically connected to the generator, is controlled by the controller.

8. A method of operation of the hydraulic system according to claim 1, the method comprising: during delivery of pressurized hydraulic fluid from the source of hydraulic pressure to the hydraulic load, controlling the hydraulic resistance of the recovery circuit with the controller based on one or more of: the value of the hydraulic flow to the hydraulic load, the hydraulic pressure at the hydraulic load, and a pressure drop across the orifice.

9. A hydraulic system, comprising: a source of hydraulic pressure; a hydraulic load; an energy recovery circuit, comprising: a first hydraulic channel including an orifice, the first hydraulic channel connecting the source of hydraulic pressure to the hydraulic load, and a recovery channel connected to the orifice at a first end and connected to a hydraulic motor at a second end; and a controller configured to control a hydraulic resistance of the recovery circuit based on one or more of a hydraulic flow to the hydraulic load, a hydraulic pressure at the hydraulic load, and a pressure drop across the orifice, the controller comprising one or more pressure controllable hydraulic valves, one pressure controllable hydraulic valve configured to fluidly connect and disconnect a first hydraulic steering chamber in a hydraulic cylinder with the recovery channel, a second steering chamber of the hydraulic cylinder continuously fluidly connected with the recovery channel, and a position of a steering element controlled depending on a comparison of the pressure in the first and second steering chamber.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) The presently proposed hydraulic system is further described and explained on the basis of figures of a drawing, wherein

(2) FIG. 1 shows a hydraulic circuit with a controller controlling an electric generator,

(3) FIG. 2 shows a hydraulic circuit with a controller acting on a hydraulic motor and

(4) FIG. 3 shows a hydraulic circuit with a controller which is at least partially working hydraulically and acting on a hydraulic motor.

(5) FIGS. 1-3 are shown approximately to scale.

DETAILED DESCRIPTION

(6) FIG. 1 shows a hydraulic system with a source 1 of hydraulic pressure which is fluidly connected with a hydraulic load 2 through a first hydraulic channel 3. The source of hydraulic pressure may be a hydraulic pump or a hydraulic piston or a high pressure hydraulic tank or any other source of hydraulic pressure. The hydraulic load 2 may be a hydraulic piston or a hydraulic motor or any other hydraulic element that may be driven by hydraulic pressure. The hydraulic load may be part of a fork lifter or another device for lifting or moving weights or may be a hydraulic tool like a hydraulic hammer.

(7) The first hydraulic channel 3 includes an orifice 4 wherein the term orifice may refer to a localised valve such as a throttle valve with a reduced cross section that causes a pressure drop or to any other hydraulic element causing a pressure drop, such as a nozzle, a hydraulic channel with a reduced cross section, or the like. The source of hydraulic pressure 1 is fluidly connected with the second hydraulic sensor 11 while the load 2 is fluidly connected with the first hydraulic sensor 10. The first hydraulic sensor 10 may measure a hydraulic pressure or may be directly located between the orifice 4 and the hydraulic load and measure a hydraulic flow. The second hydraulic sensor 11 may measure a hydraulic pressure. It may as well be provided between the source of hydraulic pressure and the orifice 4 and may measure a hydraulic flow through the orifice.

(8) The output lines of sensors 10, 11 may be electrically or hydraulically connected to the controller 9.

(9) A hydraulic motor 6 is fluidly connected with the source of hydraulic pressure 1 through the channel 5. The hydraulic motor 6 may be driven by the pressurized hydraulic fluid from the source of hydraulic pressure 1. On its low pressure side, the hydraulic motor 6 is fluidly connected with a low pressure fluid tank 16B. The hydraulic motor 6 is mechanically coupled with an electric generator 7. When the hydraulic motor 6 is rotating, the electric generator 7, driven by the hydraulic motor, is rotating as well and generating electric energy. A converter 12 may convert this electric energy to a DC current which may be fed into a battery 8. The energy delivered by the hydraulic motor 6 may also be stored in any other way, e.g. by compressing a gas in a tank.

(10) The converter 12 is directly controlled by the controller 9 in order to steer for example an excitation voltage of the generator 7 and control the resistance of the generator and thereby the mechanical resistance of the hydraulic motor 6. Thereby, the amount and share of hydraulic energy that is diverted or derived or drained from the source 1 of hydraulic pressure to the hydraulic motor 6 and therefore to the energy recovery circuit is controlled by the controller 9. In the same way, the share of hydraulic energy which is fed from the source 1 of hydraulic pressure to the load 2 is as well controlled by the controller 9.

(11) FIG. 2 shows a hydraulic circuit which is similar to the circuit shown in FIG. 1 but wherein the controller 9 not only acts on a converter 12 of the electric generator 7, but may as well act in addition or alternatively directly on the hydraulic motor 6. Therefore, the controller 9 is connected to the element 15 in an electric or hydraulic way when the element 15 may directly control an element of the hydraulic motor 6. Thereby, the position or angle of a mechanic element of the hydraulic motor 6, in particular the hydraulic displacement of the motor, may be controlled or as well a hydraulic valve at the entry or exit channel of the hydraulic motor 6. In effect, the resistance of an energy recovery part of the hydraulic circuit may be controlled and thereby the share of energy that is delivered to the load 2.

(12) FIG. 3 shows a hydraulic system wherein the controller is realized at least partially in a hydraulic way at least comprising a pressure controlled hydraulic valve.

(13) The hydraulic circuit comprises a source 1 of electric pressure which is fluidly connected with a hydraulic load 2 through a first hydraulic channel 3 and an orifice 4. Sensors 10, 11 may be provided as described above in order to measure the pressure values P10 (Sensor 10) and P11 (Sensor 11).

(14) The output of the first source of hydraulic pressure 1 is fluidly connected through the channel 5 to the input channel of the hydraulic motor 6. The exit channel of the hydraulic motor 6 is fluidly connected with the low pressure fluid tank 16B.

(15) The hydraulic motor is mechanically connected or coupled with the electric generator 7 which is controlled by the electric converter 12. The converter 12 is connected to an electric battery 8 where the recovered electric energy may be stored.

(16) The controller 13 works as follows: The control valve has output channels one of which is connected with the source of hydraulic pressure 1, one of which is connected with a low pressure fluid tank 16a, and one of which is connected to a steering volume 14a of hydraulic cylinder 14. Further, the hydraulic load 2 is fluidly connected with a first control input/control channel 13a of the control valve 13 through a control channel 17. The source 1 of hydraulic pressure is fluidly connected through the channels 5 and 20 with the second control input/control channel 13b of the control valve 13. Hence, at the first control input 13a, the pressure value is P10 (measured by sensor 10) and at the second control input 13b, the pressure value is P11 (measured by sensor 11). The control valve controls its proportional pressure output to the steering chamber 14a based on the pressure difference between P10 and P11. If (P11−P10)<=threshold value P*, the control valve 13 remains in the position as shown in FIG. 3. This implies that the steering chamber 14a is fluidly connected with the low pressure fluid tank 16b and not with channel 5. If (P11−P10)>P*, the control valve 13 starts to move (it is a proportional valve) towards a second position, connecting channel 5 gradually more with the steering chamber 14a, thereby varying the hydraulic displacement of the hydraulic motor, reducing the resistance of the hydraulic motor and starting the energy recovery. When the pressure drop across the orifice increases, the hydraulic displacement of the hydraulic motor increases, the resistance of the hydraulic motor decreases and the share of recovered energy increases.

(17) Thereby, the hydraulic circuit can easily be controlled by mainly hydraulic means and independent of electric means.

(18) The hydraulic circuit according to the presently proposed hydraulic system allows for recovery of excessive hydraulic energy delivered by a source of hydraulic pressure even in the working phase of a hydraulic load 2.

(19) FIGS. 1-3 show example configurations with relative positioning of the various components. If shown directly contacting each other, or directly coupled, then such elements may be referred to as directly contacting or directly coupled, respectively, at least in one example. Similarly, elements shown contiguous or adjacent to one another may be contiguous or adjacent to each other, respectively, at least in one example. As an example, components laying in face-sharing contact with each other may be referred to as in face-sharing contact. As another example, elements positioned apart from each other with only a space there-between and no other components may be referred to as such, in at least one example. As yet another example, elements shown above/below one another, at opposite sides to one another, or to the left/right of one another may be referred to as such, relative to one another. Further, as shown in the figures, a topmost element or point of element may be referred to as a “top” of the component and a bottommost element or point of the element may be referred to as a “bottom” of the component, in at least one example. As used herein, top/bottom, upper/lower, above/below, may be relative to a vertical axis of the figures and used to describe positioning of elements of the figures relative to one another. As such, elements shown above other elements are positioned vertically above the other elements, in one example. As yet another example, shapes of the elements depicted within the figures may be referred to as having those shapes (e.g., such as being circular, straight, planar, curved, rounded, chamfered, angled, or the like). Further, elements shown intersecting one another may be referred to as intersecting elements or intersecting one another, in at least one example. Further still, an element shown within another element or shown outside of another element may be referred as such, in one example.

(20) It will be appreciated that the configurations and routines disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. Moreover, unless explicitly stated to the contrary, the terms “first,” “second,” “third,” and the like are not intended to denote any order, position, quantity, or importance, but rather are used merely as labels to distinguish one element from another. The subject matter of the present disclosure includes all novel and non-obvious combinations and sub-combinations of the various systems and configurations, and other features, functions, and/or properties disclosed herein.

(21) As used herein, the term “approximately” is construed to mean plus or minus five percent of the range unless otherwise specified.

(22) The following claims particularly point out certain combinations and sub-combinations regarded as novel and non-obvious. These claims may refer to “an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and sub-combinations of the disclosed features, functions, elements, and/or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.