DE102014105127A1 - Hydraulic drive system of a mobile work machine - Google Patents

Abstract

The invention relates to a hydraulic drive system (1) for a mobile work machine, in particular an industrial truck, wherein the drive system (1) has a working hydraulic system (2) which comprises a lifting drive (3) and at least one auxiliary drive (4; 5). The hydraulic drive system (1) has a first electrically operated hydraulic unit (15) which comprises a hydraulic machine (15a) which can be operated as a pump and a motor and an electric machine (15b) which can be operated as a motor and a generator, wherein the first hydraulic unit (15) to supply the lifting drive (3) in lifting operation and energy recovery of the sink energy in sink operation of the lifting drive (3) is provided, wherein the energy recovery of the sink energy in sink operation, the electric machine (15b) operates as a generator and feeds electrical energy into a battery. The hydraulic drive system (1) has a second electrically operated hydraulic unit (16) which comprises a hydraulic machine (16a) which can be operated as a pump and an electric machine (16b) which can be operated as a motor, wherein the second hydraulic unit (16) supplies the lifting drive (3) in the lifting operation and to supply the auxiliary drive (4; 5) and / or a hydraulic steering device (6) is provided. An electronic control device (50) performs in the lowering operation of the lifting drive (3) on the electric machine (15b) of the first hydraulic unit (15) by a torque control by a power limitation to in sink mode with an energy recovery an inadmissible increase in speed of the electric machine operated as a generator ( 15b).

Description

The invention relates to a hydraulic drive system of a mobile work machine, in particular an industrial truck, wherein the drive system comprises a working hydraulics comprising a lifting drive and at least one auxiliary drive, wherein the hydraulic drive system comprises a first electrically operated hydraulic unit, which can be operated as a pump and motor hydraulic machine and an operable as a motor and generator electric machine, wherein the first hydraulic unit is provided for supplying the lifting drive in lifting operation and energy recovery of the sink energy in sink operation of the linear actuator, wherein the energy recovery of the sink energy in sink operation, the electric machine operates as a generator and electrical energy in a battery is fed, and wherein the hydraulic drive system comprises a second electrically operated hydraulic unit, which can be operated as a pump hydraulic machine and as a motor operable electric machine comprises, wherein the second hydraulic unit is provided for supplying the lifting drive in the lifting operation and for supplying the auxiliary drive and / or a hydraulic steering device.

Such drive systems are used in battery-powered electrical machines, such as industrial trucks. If two hydraulic power units are provided to supply the load of the working hydraulics, one of which is used to supply the lifting drive in lifting operation and for energy recovery in lowering operation of the lifting drive, the so-called Nutzsenken, and the other hydraulic unit also to power the lifting drive in lifting operation and Supply the auxiliary consumers of the working hydraulics is used, it is possible during energy recovery by the first hydraulic unit in the sink operation, the auxiliary consumers that are supplied by the second hydraulic unit to operate.

A generic hydraulic drive system is from the DE 198 31 828 B4 known. The drive system of DE 198 31 828 B4 has a hydraulic unit, which consists of a hydraulic pump and an electric motor and is provided for the supply of the lifting drive and the auxiliary load of the working hydraulics. In order to achieve high lifting speeds of the lifting drive, another hydraulic unit is provided, which is switched on when the delivery volume of the first hydraulic unit is not sufficient for the desired lifting speed. The further hydraulic unit is formed by a hydraulic machine, which can be operated as a pump and as a motor, and an electric machine, which can be operated as a motor and generator. The other hydraulic unit is used in pump mode exclusively for the supply of Hubantriebs and motor operation for energy recovery in sink mode, wherein the potential energy of a raised load is converted into electrical energy, which is fed into a battery.

In the DE 198 31 828 B4 In the lowering operation of the lifting drive, the entire lowering volume flow is fed to the further hydraulic power unit for energy recovery. The energy which is present when lifting a load with the lifting drive in the form of potential load is thus completely supplied to the further hydraulic unit when lowering. However, complete recuperation of the sink energy presupposes that the available potential energy in the electric machine of the further hydraulic unit can be converted into electrical energy and can be absorbed by the battery via a power electronics controlling the electric machine.

In this case, however, problems can occur if the hydraulic energy stored for energy recovery is significantly greater than the energy that can be delivered by the electric machine of the hydraulic unit used for energy recovery. Such a state occurs in particular in drive systems, in which two identical hydraulic units are used for cost reasons and to achieve a small number of parts and have the hydraulic machine of the two hydraulic units substantially equal displacement volume and the two electric machines of the two hydraulic units are identical. In pump operation, the two hydraulic units together generate the total power, in particular for lifting a load with the lifting drive. For energy recovery in sink operation, only one of the two hydraulic units is used for energy recovery, so that with the other hydraulic unit, a parallel operation of the auxiliary consumers is possible.

In sink mode for energy recovery occur in such drive systems, the following problems.

At maximum lowering speed of the lifting drive, wherein the sink volume flow at the hydraulic unit used for energy recovery is equal to or greater than twice the lifting volume flow of this hydraulic unit, occurs at a very high speed of the hydraulic machine operated as a motor and operated as a generator electric machine. The energy stored in the lifting drive can often not be fully utilized in the relatively short period of time because the hydraulic power pack can not convert the full potential energy because characteristics such as the maximum allowable speed and power consumption of the electric machine, the power electronics controlling the electric machine, and the charging speed of the battery prohibit the complete energy conversion.

The present invention has for its object to provide a generic drive system with two hydraulic units available, with the energy recovery in sink operation within the parameters maximum speed and power consumption of the electric machine used for energy recovery hydraulic unit is possible.

This object is achieved in that an electronic control device is provided, which performs a power limitation in the lowering operation of the linear actuator to the electric machine of the first hydraulic unit by a torque control to prevent sink operation with an energy recovery an unacceptable increase in the speed of the electric machine operated as a generator , According to the invention, the electric machine of the hydraulic unit used for energy recovery is thus operated within the permissible speeds in lowering operation and there is a power limit on the electric machine during the energy recovery. As a result, within the characteristics maximum permissible speed and power consumption of the electric machine, a partial recuperation of energy when lowering a load of the lifting drive and a return of the electrical energy generated in the battery can be achieved.

According to a preferred embodiment of the invention takes place in sink operation with energy recovery energy recovery only up to a limit speed of the electric machine operated as a generator and the excess sink energy is throttled. In the drive system with two hydraulic units can thus be an energy recovery with a hydraulic unit, which is operated for energy recovery within the allowable speeds. Thus, according to the invention, there is only a partial recuperation of the potential energy into electrical energy, the excess potential energy being throttled.

According to an advantageous embodiment of the invention, the hydraulic machine is designed as adjustable in the displacement volume adjusting machine, the displacement volume of the electronic control device is adjustable, is supported in the sink operation with an energy recovery of the sink flow completely to the adjusting, wherein in a connecting line of the lifting drive with the hydraulic Machine is arranged a drain valve with a metering orifice, which is operable according to the operation of a default device, in particular a joystick, and the drain valve is associated with a arranged in the connecting line current regulator. In conjunction with a variator with variable displacer volume, it is possible in a simple manner to supply the sink volume flow completely to the adjusting machine and to operate the electric machine within permissible rotational speeds. With the flow regulator, it is possible in a simple manner to specify the lowering speed at the lowering valve by opening the measuring orifice independently of the load pressure and to suppress the surplus energy, which can not be absorbed by the electric machine in sink operation.

With particular advantage, the electronic control device is designed such that in the lowering operation of the lifting drive the displacement volume of the hydraulic machine is increased to keep the rotational speed of the electric machine below the limit speed. By increasing the displacer volume of the adjusting in sink mode can be achieved in a simple manner that the speed of the electric machine can be kept in sink mode within reasonable levels, although the drain volume flow through the hydraulic unit is significantly higher than the lifting volume flow of this hydraulic unit.

According to an advantageous embodiment of the invention, the electronic control device is in operative connection with a pressure sensor device and the torque control is performed to limit the power of the electric machine in the sink operation on the basis of the pressures detected by the pressure sensor device. By means of a pressure sensor device, a power limitation and thus a limitation of the power consumption of the electric machine during the energy recovery can be achieved with low construction costs.

According to an advantageous embodiment of the invention, the pressure sensor device comprises a first pressure sensor, which detects the load pressure of the lifting drive between the lifting drive and the drain valve, and a second pressure sensor, which detects the pressure in the connecting line between the flow controller and the hydraulic machine, wherein in the electronic control device, a pressure difference threshold value between the detected by the first pressure sensor load pressure and the pressure detected by the second sensor is predetermined, wherein the electronic control device is designed such that when the means the pressure sensor measured pressure difference is greater than the pressure difference threshold value, the load on the electric machine is increased until the measured by means of the pressure sensors pressure difference corresponds to the predetermined pressure difference threshold. With an increase in the load of the electric machine until reaching the predetermined pressure difference threshold as the first criterion for the power limitation, a power limitation of the electric machine can be achieved in a simple manner in the sink operation via a torque control, without the lowering of the lifting drive against the sinking valve predetermined sink rate slow or stop the sinking process. Since an energy recovery only takes place as long as the measured by the pressure sensors pressure difference between the load pressure of the linear actuator and the pressure between the flow controller and hydraulic machine is greater than the predetermined pressure difference threshold, it is ensured in a simple manner that the linear actuator is lowered with the sink rate specified at the drain valve ,

P_{Rekuperation max}

die Maximal-Energierückgewinnungsleistung des Hydraulikaggregats,

V

das eingestellte Verdrängervolumen der Verstellmaschine,

n

die Drehzahl der Verstellmaschine bzw. der elektrischen Maschine und

p

der maximale Druckwert für den zweiten Drucksensor ist,

kann in der elektronischen Steuereinrichtung auf einfache Weise anhand der Parameter Drehzahl n und Verdrängervolumen V der Verstellmaschine während der Energierückgewinnung der maximale Druckwert p für den zweiten Drucksensor berechnet werden. Die Drehzahl wird bevorzugt gemessen. Das Verdrängervolumen kann anhand des von der elektronischen Steuereinrichtung erzeugten Ansteuersignals einer Verdrängervolumenstelleinrichtung der Verstellmaschine oder mittels eines geeigneten Sensors erfasst werden, der die Stellung der Verdrängervolumenstelleinrichtung der Verstellmaschine erfasst. Durch die Erhöhung der Belastung der elektrischen Maschine bis zum Erreichen des berechneten Druckgrenzwertes für den zweiten Drucksensor kann somit auf einfache Weise eine Leistungsbegrenzung über eine Drehmomentregelung der elektrischen Maschine und eine Begrenzung der Leistungsaufnahme auf die Maximal-Energierückgewinnungsleistung erzielt werden. According to an advantageous embodiment of the invention, a maximum energy recovery performance of the hydraulic unit is specified in the electronic control device and calculates the electronic control device from the speed and the displacement volume of the adjusting a maximum pressure value for the second pressure sensor, wherein the load of the electric machine is increased until the pressure detected by the second pressure sensor corresponds to the calculated maximum pressure value for the second pressure sensor. In the electronic control device, a maximum energy recovery capacity of the hydraulic unit is specified as a second criterion for the line limitation in order to achieve the power limitation and thus the limitation of the power consumption of the electric machine during the energy recovery. Based on the formula P _{recuperation max} = V * n * p, in which

P _{recuperation max}

the maximum energy recovery capacity of the hydraulic power unit,

V

the set displacement volume of the adjusting machine,

n

the speed of the adjusting machine or the electric machine and

p

the maximum pressure value for the second pressure sensor is,

can be calculated in the electronic control device in a simple manner on the basis of the parameter speed n and displacer volume V of the adjusting machine during the energy recovery, the maximum pressure value p for the second pressure sensor. The speed is preferably measured. The displacer volume can be detected on the basis of the control signal generated by the electronic control device of a displacement volume adjusting device of the adjusting or by means of a suitable sensor which detects the position of the displacer volume adjusting device of the adjusting machine. By increasing the load of the electric machine until the calculated pressure limit value for the second pressure sensor is reached, it is thus possible in a simple manner to achieve a power limitation via a torque control of the electric machine and a limitation of the power consumption to the maximum energy recovery performance.

Since it is ensured on the basis of the first criterion that the load pressure of the linear actuator detected by the first pressure sensor is higher than the pressure at the second pressure sensor by the pressure difference threshold value, it is ensured in a simple manner that a pressure difference prevails over the current regulator, so that energy recovery occurs Falling the lowering speed is avoided below the specified by actuation of the drain valve sink speed or a stalling of the sinking operation is avoided.

According to an alternative embodiment of the invention, the hydraulic machine is designed as a constant-displacement machine in the displacement volume, wherein in sink mode with an energy recovery of the sink volume flow is only partially fed to the constant machine, wherein in a connecting line of the linear actuator with the hydraulic machine, a drain valve is arranged with a metering orifice , which according to the operation of a default device, in particular a joystick, is operable, and between the drain valve and the constant machine, a flow divider is arranged, which divides the sink volume flow to the constant machine and a container. In conjunction with a flow divider, it is possible in a simple manner to supply the sink volume flow of the constant machine, which has a limited maximum speed and thus a limit speed, and to operate the electric machine within permissible rotational speeds. The flow divider makes it easy to do the Excess drain volume flow, which can not be absorbed by the constant machine in the sink operation, to dissipate to the container and to reduce the excess energy that can not be recuperated.

The torque control of the electric machine for power limitation can be carried out according to an advantageous embodiment of the invention with reference to a pressure sensor device. By means of a pressure sensor device, a power limitation and thus a limitation of the power consumption of the electric machine during the energy recovery can be achieved with low construction costs.

According to an advantageous embodiment of the invention, the pressure sensor device comprises a first pressure sensor, which detects the load pressure of the linear actuator between the lifting drive and the drain valve, and a second pressure sensor, which detects the pressure in the connecting line between the drain valve and the flow divider, wherein in the electronic Control means, a pressure difference threshold between the detected by the first pressure sensor load pressure and the pressure detected by the second sensor is predetermined, wherein the load of the electric machine is increased until the electric machine reaches the limit speed and the pressure difference measured by the pressure sensor corresponds to the predetermined pressure difference threshold , With an increase in the load of the electric machine until reaching the predetermined pressure difference threshold as a criterion for the power limitation after increasing the speed of the constant machine to the speed limit can be achieved in a simple manner in sink operation via a torque control that as much as possible of the sink energy is recuperated and a Power limitation of the electric machine is achieved.

According to an alternative embodiment of the invention, the torque control and thus the regulation of the load of the electric machine is carried out by means of a volume flow sensor device.

The volume flow sensor device is advantageously arranged in a container line, which is guided from the flow divider to the container. The volumetric flow rate sensor device can thus be used to detect in a simple manner the excess volumetric flow discharged to the container at the flow divider and throttled in the sink operation, which is not supplied to the hydraulic energy recovery machine.

In the electronic control device, a volumetric flow characteristic of the drain valve is stored to limit the power consumption and thus limiting the power consumption of the electric machine in the sink operation, wherein in the sink operation of the linear actuator with actuated drain valve, the electronic control device based on the volumetric flow characteristic of the drain valve determines the drain volumetric flow and thus knows and the drain volumetric flow the sum of the volume flow detected by means of the volume flow sensor device and the volume flow over the hydraulic machine.

The volume flow over the hydraulic machine is calculated by the electronic control device expediently from the speed and the displacement volume of the constant machine. From the electronic control device, a set speed of the hydraulic machine for the volume flow is further specified. Thus, with the electronic control device, a target rotational speed within the permissible rotational speed range of the electrical machine can be predefined in a simple manner.

After reaching the target speed of the hydraulic machine, the load of the electric machine is increased until the speed of the hydraulic machine drops below the target speed. Since the electronic control device adjusts the lowering volume flow predefined on the drain valve based on the sum of the volume flow via the volumetric flow sensor device and the volumetric flow via the hydraulic machine, the decrease in the rotational speed of the electrical machine below the calculated setpoint rotational speed represents a selection criterion, so that the load and thus the torque on the electric machine is not too high.

Conveniently, the flow divider controls with a spring means the pressure drop at a Zotilungsmeßblende, which is arranged in the connecting line between the flow divider and the hydraulic machine.

According to an advantageous embodiment of the invention, a changeover valve is arranged in the connecting line between the flow controller and the hydraulic machine, which discharges the drain flow in a container depending on the load pressure of the linear actuator or passes to the hydraulic machine. With such a switching valve, it is made possible in a simple manner to switch on the energy recovery only at reasonable load pressures and especially when lowering the lifting drive without load to direct the sink flow directly into the container to allow high lowering speeds.

For this purpose, the changeover valve expediently connects the connecting line to a container line in a first switching position and connects the connecting line to the hydraulic machine in a second switching position. If the switching valve is acted upon by the load pressure of the lifting drive in the direction of the second switching position and by a spring device in the direction of the first switching position, can be determined by the bias of the spring device in a simple manner, from which load pressures the energy recovery and should be performed.

According to an expedient embodiment of the invention, a supply line is provided which connects the connecting line with a delivery line of the second hydraulic unit, wherein in the supply line a controllable by the electronic control device check valve is arranged. With such a supply line, it is possible in a simple manner to use the first hydraulic unit for the supply of the lifting drive in lifting operation and optionally to supply the auxiliary consumers. The check valve, which is actuated by the electronic control device during the energy recovery in a blocking position, this prevents in a simple manner that is fed during the energy recovery flowing in the connecting line to the hydraulic machine lowering flow through the open supply line in the delivery line of the second hydraulic unit and via a circulation pressure compensator, which is assigned to the second hydraulic unit or the control valve block of the working hydraulics flows unused to the container. In the blocking position of the check valve is thus ensured in a simple manner that the corresponding sink volume flow flows through the connecting line of the hydraulic machine of the first hydraulic unit for energy recovery.

With particular advantage, the hydraulic machine of the first hydraulic unit is associated with a reload valve. With such a reload valve is made possible in a simple manner that a running after the electric machine and thus the hydraulic machine of the first hydraulic unit can take place in which the hydraulic machine is operated in a non-pressurized circulation.

According to an advantageous embodiment of the invention, the second hydraulic unit is additionally provided to supply a hydraulic steering device, wherein a priority valve is provided for the preferred supply of the hydraulic steering device. With the second hydraulic unit, which is not used for energy recovery in sink operation, a hydraulic steering device of the working machine can be supplied with pressure medium in a simple manner, wherein by the second hydraulic unit, which can also be operated during a power recovery in the sink operation in a pump operation in conjunction With a priority valve, the preferred supply of the steering hydraulics is ensured in all operating conditions.

Further advantages and details of the invention will be explained in more detail with reference to the embodiments illustrated in the schematic figures. This shows

1 a first embodiment of the invention,

2 a second embodiment of the invention and

3 an alternative embodiment of the invention.

In the 1 is a circuit diagram of a hydraulic drive system according to the invention 1 a mobile machine, such as a truck, shown with a battery-electric drive.

The drive system 1 has a working hydraulics 2 on, which is a linear actuator 3 and at least one power take off 4 . 5 includes. The lifting drive 3 comprises at least one hydraulic lifting cylinder, which is in communication with a load-receiving means, not shown, of the working machine for lifting and lowering a load.

The working hydraulics 2 includes in addition to the linear actuator 3 at least one auxiliary drive 4 . 5 , For example, a tilt drive of a mast and / or a side shift drive for the load-carrying means.

The drive system 1 also includes next to the working hydraulics 2 a hydraulic steering device 6 ,

The lifting drive 2 and the secondary consumers 4 . 5 are controllable by means of control valves which are in a control valve block 8th are summarized. In the illustrated embodiment, a drain valve 10 for controlling the lowering movement of the lifting drive 2 shown. In the control valve block 8th is still a schematically illustrated lifting valve 11 for controlling the lifting movement of the lifting drive 2 arranged. The drain valve 10 and the lifting valve 11 may be formed as two separate control valves or as a common control valve with a lift position and a lowered position. To control the In addition to consumer 4 . 5 is each a control valve 12 . 13 in the control valve block 8th arranged. Furthermore, in the control valve block 8th a circulation pressure balance 9 arranged.

The drive system 1 has a first electrically operated hydraulic unit 15 on, which can be operated as a pump and motor hydraulic machine 15a and an electric machine operable as a motor and a generator 15b Includes with the hydraulic machine 15a is connected. The first hydraulic unit 15 is to supply the linear actuator 3 in lifting mode and for energy recovery of the sink energy in sink operation of the lifting drive 3 intended. For energy recovery of the sink energy in sink operation works the hydraulic machine 15a as a motor, which is driven by the sink volume flow. The hydraulic machine 15a drives the electric machine 15b on, which works in energy recovery as a generator and feeds electrical energy into a battery, not shown.

The hydraulic drive system 1 also has a second electrically operated hydraulic unit 16 This is a hydraulic machine that can be operated as a pump 16a and an electric machine operable as a motor 16b includes. The second hydraulic unit 16 is to supply the linear actuator 3 in lifting operation and to supply the auxiliary drives 4 . 5 intended.

The hydraulic machine 16a serves in the illustrated embodiment, continue to supply the hydraulic steering device 6 ,

The hydraulic machine 16a is formed in the illustrated embodiment as a fixed displacement pump with a constant displacement. The hydraulic machine 16a sucks pressure medium from a container 20 and promotes in a promotion line 21 in which a priority valve 22 for the preferred supply of the hydraulic steering device 6 is arranged. From the priority valve 22 leads a conveyor branch line 23 to the hydraulic steering device 6 and a conveyor branch line 24 to the control valve block 8th the working hydraulics 2 ,

The hydraulic machine that can be operated as pump and motor 15a is on a first side via a suction line 25 with the container 20 in connection. A second side of the hydraulic machine 15a is to a connecting branch forming a sinking branch 30 connected to the lifting drive 3 is guided and in the lowering valve 10 is arranged.

The drain valve 10 includes a variable orifice plate 10a and is according to the operation of a default device 31 , For example, a joystick, operable. In the connection line 30 is between the metering orifice 10a and the hydraulic machine 15a and thus in the flow direction downstream of the metering orifice 10a the lowering valve 10 a current regulator 32 arranged. The drain valve 10 , according to the operation by the default device 31 a certain opening cross section of the measuring aperture 10a releases, and the current regulator 32 allow lowering, in the case of lowering the Hubantriebs 3 a lowering volume flow independent of the load pressure of the lifting drive 3 from the opening cross section of the metering orifice 10a is given, and thus a load pressure independent lowering according to the by an operator to the default device 31 predetermined default.

In the connection line 30 is between the current regulator 32 and the hydraulic machine 15a a changeover valve 33 arranged, depending on the load pressure of the linear actuator 3 the lowering volume flow from the linear actuator 3 in the container 20 discharges or to the hydraulic machine 15a passes.

The changeover valve 33 has a first switching position 33a on, in which the connecting line 30 with a container line 35 is connected, and a second switching position 33b on, in which the connecting line 30 with the hydraulic machine 15a connected is. The changeover valve 33 is from the load pressure of the linear actuator 3 in the direction of the second switching position 33b and a spring device 34 in the direction of the first switching position 33a applied. One is the load pressure of the linear actuator 3 leading control pressure line 41 For this purpose, one is in the direction of the second switching position 33b acting control surface of the switching valve 33 connected.

In the container line 35 are a cooler device 36 and a cooler 36 immediate by-pass valve 37 arranged. From the intake pipe 25 is a return line 38 to the container line 35 upstream of the cooler 36 connected. In the intake pipe 25 is a towards hydraulic machine 15a opening check valve 39 , For example, a check valve arranged. In the return line 38 is a towards hydraulic machine 15a blocking check valve 40 , For example, a check valve arranged. The check valves 39 . 40 make sure that in hydraulic pump operation the hydraulic machine 15a Pressure medium via the suction line 25 from the container 20 sucks and during engine operation of the hydraulic machine 15a the over the hydraulic machine 15a outflowing drain volume flow via the return line 38 and the cooler 36 in the container 20 flows.

The hydraulic machine 15a is still a reload valve 42 assigned. The reload valve 42 is in the illustrated embodiment in a connecting line 30 with the return line 38 arranged connecting line and as towards the connecting line 30 opening check valve, for example, check valve formed. The reload valve 42 in conjunction with the check valve 40 allows when running the electric machine 15b a nearly non-pressurized circulation operation of the hydraulic machine 15a ,

To pump in the hydraulic machine 15a with that of the hydraulic machine 15a funded flow the lifting drive 3 and / or the secondary consumers 4 . 5 to be able to supply is a supply line 45 is provided, which is the connecting line 30 with the to the working hydraulics 2 guided subsidy branch line 24 of the second hydraulic unit 16 combines. In the supply line 45 is a check valve 46 arranged, which is an open position 46a and a blocking position 46b having. In lowering mode of the linear actuator 3 is the check valve 46 in the locked position 46b actuated. The lowering volume flow from the linear actuator 3 thus flows to the hydraulic unit 15 to. That in the locked position 46b located check valve 46 prevents in sink mode of the linear actuator, that the sink volume flow through the supply line 45 in the subsidy branch line 24 is fed and the circulation pressure balance 9 unused in the container 20 can flow out.

To pump in the hydraulic machine 15a when in the open position check valve 46 a promotion of pressure medium in the connecting line 30 towards the drain valve 10 to avoid is in the connection line 30 between the connection of the supply line 45 and the switching valve 33 a blocking valve in the direction of the switching valve 47 , For example, a check valve arranged.

Furthermore, in the supply line 45 one towards the conveyor branch line 24 opening check valve 48 , For example, a check valve, and in the delivery branch line 24 between the priority valve 22 and the connection of the supply line 45 one towards the working hydraulics 2 opening check valve 49 , For example, a check valve arranged.

An electronic control device 50 stands for control with the electrical machines 15b . 16b in connection. Furthermore, the electrical control device is used 50 for controlling and actuating the shut-off valve 46 ,

When executing the drain valve 10 as electrically controlled drain valve is the electronic control device 50 continue with the drain valve 10 for its control and operation and with the default device 31 in connection.

In the 1 are the electric machine 15b . 16b the two hydraulic units 15 . 16 preferably identical.

In the 1 is the hydraulic machine 15a designed as adjustable in the displacement volume adjusting machine whose displacement volume of the electronic control device 50 is adjustable.

In the lifting operation of the lifting drive 3 be in the drive system according to the invention 1 the total power for lifting with high lifting speeds of the two hydraulic units 15 . 16 generated. The hydraulic unit 15 is operated in pump mode. The displacer volume of the hydraulic machine designed as an adjusting machine 15a is set here to a specific displacement volume.

In lowering mode of the linear actuator 3 can with the hydraulic unit 15 an energy recovery done. The hydraulic unit 15 is operated here in the engine mode and by the electric machine 15b generates electrical energy that is fed into the battery.

To in the drive system according to the invention 1 in energy recovery in sink operation, the hydraulic power unit 15 within the parameters maximum permissible speed and power consumption of the electrical machine operated as a generator 15b to be operated by the electronic control device 50 in lowering operation of the linear actuator 3 on the electric machine 15b of the first hydraulic unit 15 through a torque control performs a power limitation. As a result, only a partial recuperation of the existing potential energy, an impermissible increase in the speed of the hydraulic power unit, takes place in the sink mode with energy recovery 15 however, it can be prevented and there will be energy recovery within the power consumption of the electric machine operated as a generator 15b achieved.

In the 1 is in sink mode with an energy recovery of the sink volume flow from the linear actuator 3 completely to the trained as an adjusting hydraulic machine 15a promoted. To the speed of the hydraulic unit 15 is kept below a limit speed, is from the electronic control device 50 in sink mode, the displacement volume of the adjusting machine with respect to the lifting operation elevated. By adjusting the adjusting to a higher displacement volume may cause an inadmissible increase in speed of the hydraulic unit 15 be prevented and during the energy recovery, the speed of the hydraulic unit 15 be kept below a predetermined limit speed n _max .

The power limitation on the electric machine 15b of the first hydraulic unit 15 by the electronic control device 50 in sink mode via a torque control. The torque control by the electronic control device 50 takes place by means of a pressure sensor device 60 connected to the electronic control device 50 is in active connection.

The pressure sensor device 60 has a first pressure sensor 61 on, the load pressure S1 of the linear actuator 3 between the lifting drive 3 and the drain valve 10 detected, and a second pressure sensor 62 on, the pressure S2 in the connecting line 30 between the current regulator 32 and the hydraulic machine 15b detected. In the illustrated embodiment, the second pressure sensor detects 62 the pressure between the current regulator 32 and the switching valve 33 ,

The operation of the power limitation and thus for limiting the power consumption of the electric machine 15b in sink mode with an energy recovery by the electronic control device 50 is as follows.

In the electronic control device 50 is not a volume flow characteristic of the sink valve 10 and the current controller 32 deposited. By a corresponding actuation of the default device 31 by the operator is a sink flow through the sink valve 10 and the current regulator 32 specified independent of load pressure.

In the electronic control device 50 a pressure difference threshold value SW is predetermined between the load pressure S1 detected by the first pressure sensor and the pressure S2 detected by the second sensor.

If the difference between the load pressure S1 and the pressure S2 is greater than the predetermined pressure difference threshold value SW, ie, S1 - S2> SW, the electronic control device 12 50 the load on the electric machine 15b is increased until the predetermined pressure difference threshold SW is reached, ie S1 - S2 = SW.

P_{Rekuperation max}

die Maximal-Energierückgewinnungsleistung des Hydraulikaggregats,

V

das eingestellte Verdrängervolumen der Verstellmaschine,

n

die Drehzahl der Verstellmaschine bzw. der elektrischen Maschine und

p

der maximale Druckwert für den zweiten Drucksensor 62 ist,

über die Parameter Drehzahl n und Verdrängervolumen V der hydraulischen Maschine 15a den maximalen Druckwert p für den zweiten Drucksensor 62. In addition, in the electronic control device 50 a maximum energy recovery power P _{recuperation max of} the hydraulic unit 15 predetermined and the electronic control device 50 calculated using the formula P _{recuperation max} = V * n * p, in which

P _{recuperation max}

the maximum energy recovery capacity of the hydraulic power unit,

V

the set displacement volume of the adjusting machine,

n

the speed of the adjusting machine or the electric machine and

p

the maximum pressure value for the second pressure sensor 62 is

via the parameters speed n and displacement volume V of the hydraulic machine 15a the maximum pressure value p for the second pressure sensor 62 ,

The speed n of the hydraulic unit 15 This is from the electronic control device 50 detected by a speed sensor, not shown. The displacement volume V of the hydraulic machine 15a can from the electronic control device 50 be detected by means of a sensor, not shown, or from the drive signal for the displacer volume adjusting device designed as an adjusting hydraulic machine 15a be determined.

From the electronic control device 50 will be the burden of the electric machine 15a in the sink mode with an energy recovery increases until the second pressure sensor 62 detected pressure S2 the calculated maximum pressure value p for the pressure sensor 62 equivalent.

During energy recovery in sink operation thus becomes the load of the electric machine 15b increases until the maximum pressure value p for the second pressure sensor 62 is reached or the difference between the load pressure S1 and the pressure S2 reaches the predetermined pressure difference threshold SW.

If the difference between the load pressure S1 and the pressure S2 exceeds the predetermined pressure difference threshold value SW or the maximum pressure value p for the second pressure sensor in the case of energy recovery during sink operation 62 is exceeded, the excess sink energy, not from the electric machine 15b can be converted into electrical energy, at the current regulator 32 throttled.

In the 2 is a second embodiment of a drive system according to the invention 1 represented, wherein the same components are provided with the same reference numerals.

In the embodiment of 2 is the hydraulic machine 15a of the hydraulic unit 15 designed as a constant machine with a constant displacement volume.

In the 2 are the electric machine 15b . 16b and the hydraulic machines 15a . 16a the two hydraulic units 15 . 16 preferably identical.

As the displacement volume of the hydraulic machine 15a is constant and the maximum permissible speed of the hydraulic unit 15 is limited, is at the 2 in sink mode with an energy recovery only a part of the sink volume flow to the hydraulic machine 15a promoted to the speed of the hydraulic unit 15 to keep below a limit speed n _max and during the energy recovery an inadmissible speed increase of the hydraulic unit 15 to avoid.

To limit the hydraulic machine 15a in sink mode with an energy recovery inflowing maximum sink volume flow is in the embodiment of 2 between the drain valve 10 and designed as a constant machine hydraulic machine 15a a flow divider 70 is arranged, which the sink volume flow to the constant machine and the container 20 divides. The flow divider 70 is in the illustrated embodiment between the switching valve 33 and the hydraulic machine 15a arranged.

The flow divider 70 is on the input side with the connection line 30 in connection and on the output side with a section 30a the connection line 30 that to the hydraulic machine 15a is guided, as well as one to the container 20 guided tank line 71 , The container line 71 is in the illustrated embodiment of the container line 35 upstream of the cooler 36 connected. The flow divider 70 controls with a spring device 72 the pressure drop across an allotment meter 73 that in the section 30a the connection line 30 between the flow divider 70 and the hydraulic machine 15a is arranged. The flow divider 70 with the apportionment meter 73 thus limited in sink mode that of the hydraulic machine 15a for the energy recovery inflowing sink volume flow. The excess volume flow is at the flow divider 70 from the pressure level of the pressure sensor S2 to the container 20 throttled.

The power limitation on the electric machine 15b of the first hydraulic unit 15 by the electronic control device 50 in sink mode via a torque control. The torque control by the electronic control device 50 takes place by means of a pressure sensor device 60 connected to the electronic control device 50 is in active connection. The pressure sensor device 60 is analogous to the 1 from the two pressure sensors 61 and 62 ,

The operation of the power limitation and thus for limiting the power consumption of the electric machine 15b in sink mode with an energy recovery by the electronic control device 50 in the 2 is as follows.

In the electronic control device 50 is not a volume flow characteristic of the sink valve 10 and the current controller 32 deposited. By a corresponding actuation of the default device 31 by the operator is a sink flow through the sink valve 10 and the current regulator 32 specified independent of load pressure.

In the electronic control device 50 a pressure difference threshold value SW is predetermined between the load pressure S1 detected by the first pressure sensor and the pressure S2 detected by the second sensor.

Furthermore, in the electronic control device 50 a limit speed n _max for the hydraulic unit 15 and thus for the electric machine 15a deposited.

The electronic control device 50 continues to record the speed of the hydraulic unit 15 ,

If the speed of the hydraulic unit 15 is not equal to zero, is from the electronic control device 50 the load on the electric machine 15b is increased until the predetermined pressure difference threshold SW is reached, ie S1 - S2 = SW.

Unless the electric machine 15a or the hydraulic unit 15 reaches the limit speed n _max and the means of the pressure sensors 61 . 62 measured pressure difference corresponding to the predetermined pressure difference threshold SW, is from the flow divider 70 the excess drain volume flow that is not from the hydraulic power unit 15 is absorbed for energy recovery, from the Pressure level of the pressure sensor S2 to the tank 20 throttled.

In the 3 is an alternative embodiment of 2 represented, wherein the same components are provided with the same reference numerals.

In the 3 Torque control is used to limit the power and limit the power consumption of the electrical machine 15b by the electronic control device 50 instead of the pressure sensor device 60 of the 2 by means of a volume flow sensor device 75 that with the electronic control device 50 is in active connection. The volumetric flow sensor device 75 is in the container line 71 of the flow divider 70 arranged and detects the over the container line 71 outflowing excess sink volume flow when lowering with an energy recovery.

The operation of the power limitation and thus for limiting the power consumption of the electric machine 15b in sink mode with an energy recovery by the electronic control device 50 in the 3 is as follows.

In the electronic control device 50 is the volumetric flow characteristic of the sink valve 10 , which with the current regulator 32 and the metering orifice 10a load pressure independent, deposited. In sink mode, the electronic controller calculates 50 from the actuation signal of the default device 31 Based on the stored volume flow characteristic of the sink valve 10 and the current controller 32 by the operation of the default device 31 given sink volume flow.

From the electronic control device 50 becomes the sum of the volume flow sensor device 75 recorded volume flow and the volume flow through the hydraulic machine 15a adjusted with the specified drain volume flow. The volume flow through the hydraulic machine 15a is from the electronic control device 50 from the speed and displacement of the hydraulic machine 15a calculated. From the electronic control device 50 becomes a target speed of the hydraulic unit 15 specified.

When in sink mode with an energy recovery the hydraulic power unit 15 has reached the target speed is from the electronic control device 50 the load on the electric machine 15b increased until the speed of the hydraulic unit 15 falls below the setpoint speed again.

Because of the volume flow sensor device 75 at the flow divider 70 to the container 20 throttled excess sink volume flow is detected, may be from the drop in the speed of the hydraulic unit 15 be derived below the target speed as a selection criterion that the engine torque is too high, and thus the decrease in the speed of the hydraulic unit 15 below the target speed for the power limit of the electric machine 15b be used.

If the engine torque were further increased, the pressure drop (Δp) at the metering orifice would increase 10a the lowering valve 10 no longer from the current regulator 32 be determined and the sink volume flow would be lower, so that would set a sink rate below that by the operation of the sink valve 10 given lowering speed would be. The sum of the volume flow device 75 measured volume flow and the volume flow through the hydraulic machine 15a would thus be smaller than that by the operation of the drain valve 10 predetermined drain volume flow, so that the sink speed would fall below the predetermined sink speed. The of the volume flow device 75 measured volume flow thus represents a selection criterion for the power limitation, so that the engine torque is not too high.

With the drive system according to the invention 1 makes it possible, when using two, preferably identical or with identical electric machines 15b . 16b provided hydraulic units 15 . 16 , both together to power the linear actuator 3 in the lifting operation to apply the overall performance and of which only one hydraulic power unit 15 for energy recovery in sink operation of the linear actuator 3 used to work with the second hydraulic unit 16 in lowering operation of the linear actuator 3 a supply of secondary consumers 4 . 5 and an optional steering device 6 to allow some of the existing potential energy to be recovered as electrical energy and the hydraulic engine used for energy recovery 15 within the boundary conditions and parameters maximum permissible speed and maximum power consumption of the electric machine 15b to operate.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 19831828 B4 [0003, 0003, 0004]

Claims (21)

Hydraulic drive system ( 1 ) of a mobile work machine, in particular an industrial truck, wherein the drive system ( 1 ) a working hydraulics ( 2 ), which has a lifting drive ( 3 ) and at least one auxiliary drive ( 4 ; 5 ), wherein the hydraulic drive system ( 1 ) a first electrically operated hydraulic unit ( 15 ), which can be operated as a pump and motor hydraulic machine ( 15a ) and operated as a motor and generator electric machine ( 15b ), wherein the first hydraulic unit ( 15 ) for the supply of the lifting drive ( 3 ) in lifting operation and for energy recovery of the sink energy in sink operation of the linear actuator ( 3 ) is provided, wherein the energy recovery of the sink energy in sink operation, the electric machine ( 15b ) operates as a generator and feeds electrical energy into a battery, and wherein the hydraulic drive system ( 1 ) a second electrically operated hydraulic unit ( 16 ), which is a hydraulic machine which can be operated as a pump ( 16a ) and an electric machine operable as a motor ( 16b ), wherein the second hydraulic unit ( 16 ) for the supply of the lifting drive ( 3 ) in the lifting operation and for the supply of the auxiliary drive ( 4 ; 5 ) and / or a hydraulic steering device ( 6 ), characterized in that an electronic control device ( 50 ) is provided in the lowering operation of the linear actuator ( 3 ) on the electric machine ( 15b ) of the first hydraulic unit ( 15 ) performs a power limitation by means of a torque control in order, in sink operation with an energy recovery, to prevent an inadmissible increase in the speed of the electric machine ( 15b ) to prevent. Hydraulic drive system according to claim 1, characterized in that in the sink operation with an energy recovery energy recovery only up to a limit speed (n _max ) of the electric machine operated as a generator ( 15b ) takes place and the excess sink energy is throttled. Hydraulic drive system according to claim 1 or 2, characterized in that the hydraulic machine ( 15a ) is formed as adjustable in the displacement volume adjusting machine whose displacement volume from the electronic control device ( 50 ) is adjustable, wherein in the sink mode with an energy recovery of the sink volume flow is completely promoted to the adjusting machine, wherein in a connecting line ( 30 ) of the linear actuator ( 3 ) with the hydraulic machine ( 15a ) a drain valve ( 10 ) with a measuring diaphragm ( 10a ) arranged in accordance with the operation of a default device ( 31 ), in particular a joystick, and the drain valve ( 10 ) in the connecting line ( 30 ) arranged current regulator ( 32 ) assigned. Hydraulic drive system according to claim 3, characterized in that the electronic control device ( 50 ) is designed such that in the lowering operation of the lifting drive ( 3 ) the displacement volume of the hydraulic machine ( 15a ) is increased to the speed of the electric machine ( 15b ) below the limit speed (n _max ). Hydraulic drive system according to claim 3 or 4, characterized in that the electronic control device ( 50 ) with a pressure sensor device ( 60 ) is in operative connection and the torque control of the electric machine ( 15b ) in the sink operation on the basis of the pressure sensor device ( 60 ) detected pressures takes place. Hydraulic drive system according to claim 5, characterized in that the pressure sensor device ( 60 ) a first pressure sensor ( 61 ), the load pressure (S1) of the linear actuator ( 3 ) between the lifting drive ( 3 ) and the drain valve ( 10 ), and a second pressure sensor ( 62 ), the pressure (S2) in the connecting line ( 30 ) between the current regulator ( 32 ) and the hydraulic machine ( 15a ), wherein in the electronic control device ( 50 ) a pressure difference threshold (SW) between that of the first pressure sensor ( 61 ) detected load pressure (S1) and that of the second sensor ( 62 ) detected pressure (S2) is predetermined, wherein the electronic control device ( 50 ) is configured such that when the pressure difference (S1-S2) measured by means of the pressure sensors (S1, S2) is greater than the pressure difference threshold value (SW), the load of the electric machine ( 15b ) is increased until the measured by the pressure sensors (S1, S2) pressure difference (S1 - S2) corresponds to the predetermined pressure difference threshold (SW). Hydraulic drive system according to claim 6, characterized in that in the electronic control device ( 50 ) a maximum energy recovery capacity (P _{recuperation max} ) of the hydraulic power unit ( 15 ) and the electronic control device ( 50 ) from the speed (n) and the displacement volume (V) of the adjusting machine a maximum pressure value (p) for the second pressure sensor ( 62 ), the load of the electric machine ( 15b ) is increased until that of the second pressure sensor ( 62 ) detected pressure (S2) the calculated maximum pressure value (p) for the second pressure sensor ( 62 ) corresponds. Hydraulic drive system according to claim 1 or 2, characterized in that the hydraulic machine ( 15a ) as in the displacer volume constant constant machine is formed, wherein in sink mode with an energy recovery of the sink volume flow is only partially fed to the constant machine, wherein in a connecting line ( 30 ) of the linear actuator ( 3 ) with the hydraulic machine ( 15a ) a drain valve ( 10 ) with a measuring diaphragm ( 10a ) arranged in accordance with the operation of a default device ( 31 ), in particular a joystick, and between the drain valve ( 10 ) and the constant machine, a flow divider ( 70 ) is arranged, which the sink volume flow to the constant machine and a container ( 20 ). Hydraulic drive system according to claim 8, characterized in that the electronic control device ( 50 ) with a pressure sensor device ( 60 ) is in operative connection and the torque control on the basis of the pressure sensor device ( 60 ) detected pressures takes place. Hydraulic drive system according to claim 9, characterized in that the pressure sensor device ( 60 ) a first pressure sensor ( 61 ), the load pressure (S1) of the linear actuator ( 3 ) between the lifting drive ( 3 ) and the drain valve ( 10 ), and a second pressure sensor ( 62 ), the pressure (S2) in the connecting line ( 30 ) between the drain valve ( 10 ) and the flow divider ( 70 ), wherein in the electronic control device ( 50 ) a pressure difference threshold (SW) between that of the first pressure sensor ( 61 ) detected load pressure (S1) and that of the second sensor ( 62 ) pressure (S2) is predetermined, wherein the load of the electric machine ( 15b ) is increased until the electric machine ( 15b ) reaches the limit speed (n _max ) and the pressure difference (S1 - S2) measured by means of the pressure sensors (S1, S2) corresponds to the predetermined pressure difference threshold value (SW). Hydraulic drive system according to claim 8, characterized in that the electronic control device ( 50 ) with a volume flow sensor device ( 75 ) is in operative connection and the torque control using the volume flow sensor device ( 75 ) he follows. Hydraulic drive system according to claim 11, characterized in that the volume flow sensor device ( 75 ) in a container line ( 71 ) arranged by the flow divider ( 70 ) to the container ( 20 ) is guided. Hydraulic drive system according to claim 11 or 12, characterized in that in the electronic control device ( 50 ) a volumetric flow characteristic of the sink valve ( 10 ), wherein in the lowering operation of the linear actuator ( 3 ) with the lowering valve ( 10 ) the electronic control device ( 50 ) based on the volumetric flow characteristic of the sink valve ( 10 ) determines the sink volume flow and the sink volume flow with the sum of the volume flow sensor means ( 75 ) and the volume flow through the hydraulic machine ( 15a ). Hydraulic drive system according to claim 13, characterized in that the volume flow through the hydraulic machine ( 15a ) from the electronic control device ( 50 ) from the speed (n) and the displacement volume (V) of the hydraulic machine ( 15a ) and a setpoint speed of the hydraulic machine ( 15a ) is specified for the volume flow. Hydraulic drive system according to claim 14, characterized in that after reaching the setpoint speed of the hydraulic machine ( 15a ) the load of the electric machine ( 15b ) is increased until the speed of the hydraulic machine ( 15a ) drops below the target speed. Hydraulic drive system according to one of claims 8 to 15, characterized in that the flow divider ( 70 ) with a spring device ( 72 ) the pressure drop across an allotment meter ( 73 ), which in the connecting line ( 30 ) between the flow divider ( 70 ) and the hydraulic machine ( 15a ) is arranged. Hydraulic drive system according to one of claims 3 to 16, characterized in that in the connecting line ( 30 ) between the drain valve ( 10 ) and the hydraulic machine ( 15a ) a switching valve ( 33 ) is arranged, which depends on the load pressure of the linear actuator ( 3 ) the drain volume flow into a container ( 20 ) or to the hydraulic machine ( 15a ). Hydraulic drive system according to claim 17, characterized in that the switching valve ( 33 ) in a first switching position ( 33a ) the connection line ( 30 ) with a container line ( 35 ) and in a second switching position ( 33b ) the connection line ( 30 ) with the hydraulic machine ( 15a ), wherein the switching valve ( 33 ) of the load pressure of the linear actuator ( 3 ) in the direction of the second switching position ( 33b ) and a spring device ( 34 ) in the direction of the first switching position ( 33a ) is acted upon. Hydraulic drive system according to one of claims 1 to 18, characterized in that a supply line ( 45 ) is provided, the connecting line ( 30 ) with a delivery line ( 24 ) of the second hydraulic unit ( 16 ), whereby in the supply line ( 45 ) one of the electronic control device ( 50 ) controllable shut-off valve ( 46 ) is arranged. Hydraulic drive system according to one of claims 1 to 19, characterized in that the hydraulic machine ( 15b ) of the first hydraulic unit ( 15 ) a reload valve ( 42 ) assigned. Hydraulic drive system according to one of claims 1 to 20, characterized in that the second hydraulic unit ( 16 ) in addition to supplying a hydraulic steering device ( 6 ), wherein the preferred supply of the hydraulic steering device ( 6 ) a priority valve ( 22 ) is provided.

Images