DE102007007337A1 - Hydraulic system for recovering free releasing energy, has hydraulic pump including connection connected with hydraulic consumer, and another connection connected with tank volume and hydraulic lifting device for lifting weight - Google Patents

Abstract

The system (1) has a hydraulic pump (2) including a connection (3) connected with a hydraulic consumer (7), and another connection (4) connected with a tank volume (5) and a hydraulic lifting device (20) for lifting a weight (27). The connection (4) is connected with the tank volume via a suction line (6) and a return valve (29). The return valve opens in a direction toward the hydraulic pump and is arranged in the suction line. The hydraulic lifting device is connected with the hydraulic pump by a storage line (19).

Description

The The invention relates to a hydraulic recovery system of released energy.

at Construction machinery such as excavators often becomes one Working hydraulics by a hydraulic pump with pressure medium for lifting charged by loads. For example, stem and outrigger positioned by using hydraulic cylinders. While for lifting a load by the hydraulic pump pressure medium under high Pressure must be provided, vice versa Lowering a load, the pressurized fluid from the hydraulic cylinder repressed. It is usually about a Throttle in a tank volume relaxed to the lowering movement slow it down. The released potential energy is thereby in Heat converted.

To store such released kinetic energy, it is in the JP 01-127730 A proposed to provide an additional hydraulic cylinder between the boom and the uppercarriage of an excavator. This additional hydraulic cylinder displaces the pressure medium located in a working chamber of the cylinder in another cylinder when lowering the boom. With the help of this additional cylinder, a counterweight of the excavator is raised and thus the energy released when lowering the boom stored by lifting the counterweight as potential energy. Conversely, the counterweight can be lowered again and with the pressure generated by the hydraulic cylinder arranged there, a lifting movement of the boom can be supported.

adversely in the known system for energy recovery, it is that an additional hydraulic cylinder between the boom and the superstructure is required. This additional Hydraulic cylinder is also with the cylinder for lifting the counterweight connected in a separate hydraulic circuit. With it rises not only the expense of producing the overall hydraulic system, but two separate hydraulic circuits have to be created be, with the amount of hydraulic fluid required increases. In addition, the return is the stored potential energy only to raise the boom again possible. The benefits of stored energy for other movements are not possible.

It Therefore, the object of the invention is a hydraulic system for Recovery of released energy to create which is simpler in terms of its structure and also more flexible Usage possible.

The Task is by the inventive hydraulic Recovery system of energy released according to claim 1 solved.

According to the invention the hydraulic system for the recovery of released Energy at least one hydraulic consumer and a hydraulic pump. The hydraulic pump has a first port and a second port on. The first connection of the hydraulic pump is the hydraulic consumer connected. The second connection of the hydraulic pump, however, is with a tank volume and a hydraulic lifting device for lifting a weight connected. With the inventive design of the hydraulic system, it is possible the released To supply energy directly from the working hydraulics to the storage and the potential energy stored by lifting the weight attributed to the hydraulic pump. This can do this Energy are supplied to each hydraulic consumer, which is connected to the hydraulic pump.

Especially It is also possible to have several hydraulic consumers over to operate a common hydraulic pump. That way can not only in a hydraulic consumer released energy in Form of potential energy stored by lifting the counterweight but it can be used both in storing the released energy as well as in the recovery of the stored energy all connected hydraulic Consumers are used.

In the dependent claims are advantageous developments of according to the invention executed hydraulic system.

Especially it is advantageous to the hydraulic pump via a suction line to connect with the tank volume, wherein in the suction line in Direction to the hydraulic pump opening check valve is arranged. By providing a check valve in the suction line is on the one hand automatically for storage of Energy pressure fluid supplied to the hydraulic lifting device. On the other hand, pressure medium is automatically sucked from the tank volume, if z. B. at the end of a Rekuperationsvorgangs the weight already again lowered to its lowest level and further pressure medium not available from the hydraulic lifting device stands.

The lifting device is preferably connected via a storage line to the hydraulic pump, wherein the storage line between the check valve and the second port in the suction line opens. With the outflow of the storage line between the check valve and the The second connection of the hydraulic pump is automatically switched between the tank volume and the hydraulic lifting device both for storage and for the recovery of energy. An active intervention in the pressure medium flow is not required.

The Hydraulic lifting device preferably comprises at least one Hydraulic cylinder. Further, the hydraulic pump is preferably as in two-way adjustable hydraulic pump designed. This can both for storing the energy as well as in the recovery the energy the delivery volume be adjusted. Especially is it possible to have a larger volume flow towards the working hydraulics, so the hydraulic consumer too generate, as in an exclusive use of the hydraulic jack available Volumetric flow is the case.

Of the hydraulic consumer preferably comprises a double-acting Hydraulic cylinder with two working chambers, which have one Valve device are connected to the hydraulic pump. Especially can also have multiple identical hydraulic consumers over a valve block with the hydraulic pump or the first port of Be connected hydraulic pump.

The Using a valve block has the advantage of having the connection between the hydraulic pump and the respective hydraulic consumer can be flexibly controlled. This is the energy flows from both the hydraulic consumers to the hydraulic jack as well as in the opposite direction independently controllable.

A preferred embodiment of the invention hydraulic system is shown in the drawing and will explained in more detail in the following description. Show it:

1 a hydraulic circuit diagram of an embodiment of the hydraulic system according to the invention;

2 a schematic representation of the hydraulic system according to the invention in a rest position;

3 a second representation of the hydraulic system according to the invention during storage of released energy;

4 a third view of the hydraulic system according to the invention during the return of the stored energy; and

5 a schematic representation of a profile of the flow rates during an exemplary work cycle.

In the 1 is a hydraulic system according to the invention 1 shown. The hydraulic system 1 includes a hydraulic pump 2 , The hydraulic pump 2 is designed for two-way delivery and adjustable in volume. The hydraulic pump 2 has a first connection 3 and a second connection 4 on. For lifting, for example, a boom of an excavator sucks the hydraulic pump 2 over the second connection 4 from a tank volume 5 Pressure medium on. The second connection 4 the hydraulic pump 2 is via a suction line 6 with the tank volume 5 connected. That through the hydraulic pump 2 funded pressure medium is a double-acting hydraulic cylinder 7 supplied as a hydraulic consumer. The double-acting hydraulic cylinder 7 includes a working piston 8th , The working piston 8th has a bottom-side piston surface 9 and a rod-side piston surface 10 on. The bottom-side piston surface 9 and the rod-side piston surface 10 are oriented in opposite directions. The working piston 8th is via a piston rod 11 For example, connected to the boom of an excavator to support this and move.

The bottom-side piston surface 9 is in a first working chamber 12 acted upon by a pressure medium. Accordingly, for generating an opposite adjusting movement of the adjusting piston 8th the rod-side piston surface 10 in a second working chamber 13 acted upon by a control pressure. For generating a setting pressure in the first working chamber 12 or in the second working chamber 13 are the first working chamber 12 and the second working chamber 13 over a first working line 14 or a second working line 15 connected to a valve device. The valve device is in the illustrated embodiment as a directional valve 16 executed. The directional valve 16 is a 3/3-way valve. The directional valve 16 is via a support line 17 with the first connection 3 the hydraulic pump 2 connected. In a first end position, the directional valve connects 16 the support line 17 with the first working line 14 , In this switching position of the directional valve 16 This is the result of the hydraulic pump 2 from the tank volume 5 sucked pressure medium via the first working line 14 the first working chamber 12 fed. This will be the actuator piston 8th in the 1 shifted upward and raised, for example, the boom of an excavator.

At the same time is through the directional valve 16 in the first switching position, the second working line 15 with a return line 18 connected. The return line 18 connects the directional valve 16 with the tank volume 5 , To compensate for the smaller expectant volume of the second working chamber 13 during a lifting movement of the double-acting hydraulic cylinder 7 the pressure medium from the second working chamber 13 about the second working line 15 in the tank volume 5 relaxed.

With reverse control of the directional valve 16 on the other hand, the support line 17 with the second working line 15 and the first working line 14 with the return line 18 connected. Accordingly, an opposite actuating movement of the actuating piston 8th and thus the piston rod 11 or of the boom connected thereto.

In the suction line 6 is a check valve 29 arranged. The check valve 29 opens towards the second port 4 the hydraulic pump 2 to.

To store the energy released when lowering a load acting on the boom between the check valve 29 and the second port 4 the hydraulic pump 2 a storage line 19 with the suction line 6 connected. At the from the outlet in the suction line 6 remote end of the storage line 19 is a hydraulic lifting device 20 arranged. The storage line 19 thus connects the lifting device 20 with the suction line 6 , The hydraulic lifting device 20 includes in the illustrated embodiment, a first hydraulic cylinder 21 and a second hydraulic cylinder 22 , The first hydraulic cylinder 21 and the second hydraulic cylinder 22 are identical. The elements described below are therefore only in connection with the first hydraulic cylinder 21 described. The comparable elements of the second hydraulic cylinder 22 are provided with corresponding, primed reference numerals.

In the first hydraulic cylinder 21 is a reciprocating piston 23 arranged. The reciprocating piston 23 has a Hubkolbenfläche 24 on that a pressure room 25 limited. The pressure room 25 is via a first line branch 19 ' the storage line 19 with the suction line 6 connected.

In a corresponding manner is via a second line branch 19 '' the pressure room 25 ' of the second hydraulic cylinder 22 with the suction line 6 connected.

For storing on the double-acting hydraulic cylinder 7 released energy is through the first hydraulic cylinder 21 and the second hydraulic cylinder 22 together a weight 27 raised. The weight 27 is preferably the counterweight of an excavator. The stroke direction, ie the orientation of the first hydraulic cylinder 21 and the second hydraulic cylinder 22 is preferably chosen so that a lifting movement is supported by a rotational movement of the excavator. For this purpose, the stroke direction is not aligned identically with the vertical, but extends with a radial component with respect to a rotational axis of a rotating mechanism of the excavator, so that a rotational movement of the upper carriage of the excavator for lifting the weight 27 required force reduced.

In the storage line 19 is a holding valve 30 intended. The holding valve 30 is a 2/2-way valve, which in a first position an unthrottled connection of the pressure chambers 25 . 25 ' with the suction line 6 allows. In his second, in the 1 The position shown assumes the holding valve 30 the function of one towards the hydraulic jack 20 opening check valve. In this position, a flow of pressure medium from the pressure chambers 25 . 25 ' prevented. The function of the holding valve 30 can also be operated by a hydraulic pump for short switching cycles 2 be taken over. The hydraulic pump 2 is then designed as a pressure holding pump.

For actively generating one by the hydraulic lifting device 20 stored potential energy is in a middle position of the directional valve 16 the return line 18 with the support line 17 connected. This allows the hydraulic pump 2 directly from the tank volume 5 Pressure medium via the return line 18 and the support line 17 suck. This pressure medium is through the hydraulic pump 2 over the suction line 6 in the storage line 19 and thus the pressure chambers 25 . 25 ' promoted. As a result, the weight becomes 27 raised and potential energy stored there.

The control of the directional valve 16 and the holding valve 30 is preferably carried out electromagnetically. However, it is conceivable that the control takes place via control pressures at the directional valve 16 or the holding valve 30 acts on corresponding control surfaces of the valves.

The function of storing and recovering energy will be described below with reference to FIGS 2 to 4 explained. To explain the function was in the 2 to 4 on a representation of the details of the hydraulic system, as in the 1 was explained waived.

In the 2 the hydraulic system is shown in a starting position. The hydraulic pump 2 is set to a zero delivery volume. As a result, there is no volume flow in the delivery line 17 and the storage line 19 and the working piston 8th and the reciprocating piston 23 standing still. In the pressure room 25 and the first working chamber 12 For example, there is a pressure of 250 bar.

Was by the power piston 8th lifted a weight, so when lowering the weight, the potential energy released there by the hydraulic lifting device 20 be saved as it is in the 3 is shown schematically. On the left side of the 3 It is indicated by an arrow that exerts a force on the piston rod 11 acts and thus the working piston 8th in the 3 with z. B. 1 m / sec moves down. It is characterized by the bottom-side piston surface 9 a pressure on that in the first working chamber 12 located pressure medium exerted. This pressurized pressure medium is via the delivery line 17 the hydraulic pump 2 fed. The hydraulic pump 2 is for example at 10% of its maximum delivery volume in the direction of the storage line 19 deflected out. Because of the hydraulic pump 2 subsidized pressure medium, the counterweight is raised accordingly. Unless the size ratios of the working chamber 12 and the pressure chamber 25 and the working piston 8th and the reciprocating piston 23 Correspond to each other, thus becomes the counterweight 27 lifted at the same speed with which the boom is lowered. It is assumed that a leakage volume flow of the hydraulic pump 2 from the tank volume 5 via the return line 18 is fed again. In the first working chamber 12 and the pressure room 25 in each case there is a pressure of 250 bar and the volume flows from the first working chamber 12 and in the pressure chamber are each 100 l / min.

By using an adjustable hydraulic pump 2 However, it is also possible, the lowering speed and the lifting speed of the counterweight 27 to choose differently. For example, in the 3 the delivery volume of the hydraulic pump 2 to 50% of the maximum delivery volume towards the storage line 19 set, so complement one from the working chamber 12 escaping flow and via the return line 18 supplied volume flow. The pressure room 25 Ultimately, a volume flow is supplied, which is the sum of the volume flow from the working chamber 12 and via the return line 18 supplied volume flow less the leakage volume flow corresponds. For example, if a volume flow of 100 liters per minute from the first working chamber 12 by a volume flow from the tank volume 5 added to the return line in the amount of 50 l per minute and assumed a leakage volume flow of 10 l per minute, so is ultimately the pressure chamber 25 a volume flow of 140 liters per minute supplied. The pressure in the first working chamber 12 is 250 bar at a sink rate of the working piston 8th of 1 m / sec. In the pressure room 25 By contrast, at a lifting speed of 1.5 m / sec, a pressure of 250 bar prevails.

Accordingly, the sinking rate is on the part of the working piston 8th less than the lifting speed of the reciprocating piston 23 ,

In the 4 is exemplary of the recovery of the stored potential energy by the hydraulic lifting device 20 shown. It is first assumed that the counterweight drops at a speed of 1 m per second. In the pressure room 25 there is a pressure of 250 bar. Pressure medium with a volume flow of 100 liters per minute is discharged from the pressure chamber and the second connection 4 the hydraulic pump 2 fed. The hydraulic pump 2 is now swung in the opposite direction and promotes the over the storage line 19 and the second port 4 supplied pressure medium in the delivery line 17 , In the promotion line 17 Also, a volume of 100 liters per minute is achieved, that of the first working chamber 12 is supplied. The first working chamber 12 stands under a pressure of 250 bar and raises the boom at a speed of 1 m per second. The leakage volume, which in turn is 10 l per minute, for example, is via the suction line 6 from the tank volume 5 fed. The hydraulic pump again stands at 10% of its maximum delivery volume.

The supply of the required leakage volume is carried out automatically via the check valve 29 ,

On the other hand, if a larger lifting speed on the side of the working hydraulics so the double-acting hydraulic cylinder 7 be achieved, then the hydraulic pump 2 to a larger delivery volume in the direction of the delivery line 17 swung out. If, for example, the delivery volume of the hydraulic pump 2 set to 50% of the maximum flow rate, in addition to the volume flow of 100 l per minute, which is from the pressure chamber 25 (250 bar) is provided, additional pressure medium from the tank volume 5 sucked. This pressure medium from the tank volume 5 For example, it can reach 50 liters per minute. This will be after deduction of the leakage volume flow 10 l per minute of the delivery line 17 a volume flow of 140 liters per minute supplied. This volume flow generated in the first working chamber 12 a pressure of 280 bar. The boom is lifted at a speed of 1.5 m per second. Thus, by adjusting the delivery volume, the hydraulic pump 2 the speed of movement of the working piston 8th relative to the speed of the reciprocating piston 23 the hydraulic lifting device 20 adjust. This can be for both the storage of energy as well as the recovery of energy are carried out. The selected numerical examples are merely illustrative.

A schematic representation of a curve of the pressures and the volume flows is the 5 shown. A raising and lowering of a boom, with the piston rod 11 of the double-acting hydraulic cylinder 7 is divided into a total of six sections I to VI. The course of the top line 35 gives the pressure in the first working chamber 12 again.

The course of the second line 36 On the other hand, it sets the volume flow into or out of the first working chamber 12 dar. The third course 37 corresponds to the volume flow from the pressure chamber 25 or into it. The fourth course 38 gives an additional volume flow from the tank volume 5 at. In the second region II, the boom is lifted by a constant volume flow into the first working chamber 12 into it. At constant pressure, a constant lifting speed is achieved. The one in the first working chamber 12 flowing in flow rate is made up of a pressure medium amount of the pressure chamber 25 and a supplementary amount of pressure medium from the tank volume 5 together. While initially only pressure medium from the pressure chamber 25 the lifting cylinder 21 taken and the first working chamber 12 is fed towards the end of the recovery of the stored potential energy when the volume of the pressure chamber 25 has already been used up, a quantity of pressure medium from the tank volume 5 added.

In section III, first, the deceleration of the lifting movement of the boom of the excavator is shown before the boom is held in a constant position. Subsequently, in the area IV, the transition to a lowering of the boom, which is indicated in the area V at a constant speed. It is stated that during the lowering of the working cylinder 7 in the first working chamber 12 a reduced pressure prevails. That from the first working chamber 12 displaced pressure medium is the lifting cylinder 21 . 22 and thus the pressure room 25 . 25 ' fed. This will be the weight 27 lifted and on the hydraulic consumer so the double-acting hydraulic cylinder 7 released energy in the form of potential energy through the hydraulic lifting device 20 saved.

The Invention is not on the illustrated embodiment limited. In particular, combinations of individual Features of the invention possible with each other.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• JP 01-127730 A [0003]

Claims (7)

Hydraulic system for recovering released energy with at least one hydraulic consumer ( 7 ) and a hydraulic pump ( 2 ) with a first connection ( 3 ) and a second connection ( 4 ), the first connection ( 3 ) of the hydraulic pump ( 2 ) with the hydraulic consumer ( 7 ) and the second port ( 4 ) with a tank volume ( 5 ) and a hydraulic lifting device ( 20 ) for lifting a weight ( 27 ) connected is. Hydraulic system according to claim 1, characterized in that the second connection ( 4 ) of the hydraulic pump ( 2 ) via a suction line ( 6 ) with the tank volume ( 5 ) and in the suction line ( 5 ) in the direction of the hydraulic pump ( 2 ) opening check valve ( 29 ) is arranged. Hydraulic system according to claim 2, characterized in that the hydraulic lifting device ( 20 ) via a memory line ( 19 ) with the hydraulic pump ( 2 ) and the memory line ( 19 ) between the check valve ( 29 ) and the second connection ( 4 ) in the suction line ( 6 ). Hydraulic system according to one of claims 1 to 3, characterized in that the hydraulic lifting device ( 20 ) at least one hydraulic cylinder ( 21 . 22 ). Hydraulic system according to one of claims 1 to 4, characterized in that the hydraulic pump ( 2 ) is provided for conveying in two directions. Hydraulic system according to claim 5, characterized in that the hydraulic pump ( 2 ) is adjustable in its delivery volume. Hydraulic system according to one of claims 1 to 6, characterized in that the hydraulic consumer ( 7 ) comprises a double-acting hydraulic cylinder whose two working chambers ( 12 . 13 ) via a valve device ( 16 ) with the hydraulic pump ( 2 ) are connectable.