DE102006060351B3 - Hydraulic circuit arrangement for battery-driven industrial truck, has priority valve arranged to distribute volume flow flowing from pump to cylinder and load, and motor and pumps designed as motor-dual pump assembly - Google Patents

Abstract

The arrangement has a pump (P1) attached to a lifting cylinder (HZ) and driven by an electric motor (M/G). The motor serving as a generator and the pump serving as a hydro motor are operated for regeneration of potential energy of the cylinder. The motor and pumps (P1, P2) are designed as a motor-dual pump assembly. A priority valve (PRV) is arranged between the pump (P1) and the cylinder to distribute a volume flow flowing from the pump (P1) to the cylinder and a load (Z1). The valve distributes the volume flow flowing back from the cylinder corresponding to the load and the pump (P1).

Description

The The invention relates to a hydraulic circuit arrangement with a driven by an electric motor, associated with a lifting cylinder first pump, wherein the energy recovery of Electric motor as a generator and the first pump operated as a hydraulic motor are to recover potential energy of the lifting cylinder, and with a second Pump for supplying at least one further consumer according to the preamble of claim 1.

Such a circuit arrangement for battery-powered trucks is from the DE 43 17 782 C2 known. Therein drives a DC or asynchronous electric motor, a pump P, which provides the hydraulic pressure for the lifting cylinder. When lowering the load, the circuit arrangement releases a path on which the fluid can flow back from the lifting cylinder to the pump P with virtually no pressure loss. In this case, the potential energy stored in the lifting cylinder is recovered by the pump now working as a hydraulic motor and the electric motor as a generator G for recharging the battery. The particular advantages are that the effort is relatively low and no principle-related pressure losses occur.

In the known arrangement, even more consumers can be connected. For this purpose, a separate circuit with a further pump and its own drive motor is provided. In addition, additional functions can be operated by the former working group. For this purpose, however, the lowering function must be interrupted in each case DE 299 11 686 U1 Another electro-hydraulic lifting module is known, which can be operated in a power-saving mode. Here, a single pump supplies both main and secondary consumers, which can be connected via an electromagnetically controlled valve. For the lowering of the lift cylinder own return line is provided, which connects the lifting cylinder with the suction side of the pump when released, with a check valve prevents the immediate emptying into the tank. The otherwise provided for the lifting operation working line of the pump then acts as a return line and is connected via an electromagnetic valve to the tank.

Of the Invention is based on the object, an improved, more cost-effective Circuit for energy recovery from a lifting cylinder while operating with other consumers specify.

According to the invention this is in a hydraulic circuit arrangement according to the preamble of Claim 1 achieved in that the electric motor, the first pump and the second pump as a motor double pump unit are formed, wherein the first pump in the lowering operation of the lifting cylinder works as a hydraulic motor with reversal of direction, while the second pump always as a pump with the same flow direction operates, and between the first pump and the lifting cylinder a priority valve is provided, which the flowing from the first pump flow as needed on the lifting cylinder on the one hand and on the at least another consumer on the other hand and in the lowering of the Lift cylinder backflowing volume flow according to the at least one consumer and the first Pump distributed.

These solution reduces the valve technical complexity of known circuit arrangements for Supplying several consumers quite considerably.

Preferably is in the working line of the first pump between the priority valve and the lifting cylinder arranged an electrically controllable lift valve, that with simultaneous operation of the lifting cylinder and the at least opens another consumer partially and in his two limit positions to blocking and passage of the working line of the first pump switches, with not simultaneous operation of the lift cylinder and the at least one other consumer fully opens the lift valve. The Lift valve together with the priority valve ensures that excess volume flow the first pump can flow to the other consumers, where it adds to the flow rate of the second pump. The second pump can therefore be relatively small dimensions, because they through the supported first pump becomes.

Especially is advantageous if the priority valve is designed such that it is controlled by the pressure difference occurring at the globe valve is, wherein in a first extreme position of the priority valve the first pump on the one hand over a throttle with the lift valve and on the other hand with the at least another consumer is connected, while in a second, contrary set extreme position of the priority valve that of the first Pump coming working line switched to passage and at the same time is associated with the at least one other consumer, and the priority valve also a Middle position, in which the working line of the first pump switched to passage and the line to the at least one other Consumer is locked.

Preferably, in the line leading from the priority valve to at least one further consumer, a check valve is provided, which then opens when in the from the first pump to Lift cylinder leading working line overpressure over the pressure generated by the second pump is present.

The Providing additional consumers can be beneficial over one Constant current system done, which is particularly simple and for many sufficient practical applications. Preferably, however, this can also be done a load-sensing system will be provided which provides better pressure and volume adjustment to the current requirements of individual consumers.

In Another advantageous embodiment of the invention is an electrical controllable load-lowering valve provided in the lowering operation the Volume flow from the lifting cylinder without energy recovery to the tank derived and in the cases is switched, in which waived the energy recovery should. Such a case may, for example, when lowering a small lifting load and simultaneous operation of other consumers occur. If here for the reclamation only little energy is available if appropriate, it is preferable to divert the volume flow into the tank. Such situations can preferably be detected by pressure sensors in the respective Working lines of the first and the second pump are provided and serve to control the load-lowering valve.

Further Advantages of the invention will become apparent from the following description of the figures:

It demonstrate:

1 A first embodiment of the invention, in which the other consumers are supplied via a load-sensing system.

2 : The embodiment of the 1 with a load-reducing valve for selectively bypassing the energy recovery.

3 A further embodiment in which the additional consumers are supplied via a constant current system.

In 1 a first embodiment of the invention is shown. The motor double pump unit MDP comprises an electric motor M / G, which drives a first pump P1 and a smaller-dimensioned, second pump P2, wherein the electric motor M / G and the pumps P1, P2 are arranged on a common shaft. The first pump P1 supplies the hydraulic pressure for a lifting cylinder HZ, the second pump P2 supplies additional consumers Z1, Z2.

At the Lowering the load, potential energy of the lifting cylinder HZ is recovered, wherein the first pump P1 with reversal of direction then as a hydraulic motor and the electric motor M / G as a generator for recharging a Not shown accumulator function. The second pump P2 works independently from the direction of rotation always as a pump with the same conveying direction.

The first pump P1 is slot-controlled, i. their displacement chambers are over a Valve plate alternately with the high and the low pressure side connected. Will the displacement room in the suction stroke, ie connected to low pressure during volume increase, then the unit works as a pump, it is with volume increase with connected to the high pressure then the unit works as a motor. At the Change from lifting to lowering operation of the lifting cylinder HZ changes the first operating as a pump unit P1 at substantially unchanged pressures the direction of rotation and thus simultaneously changes to the engine operation.

The Pump P2 is controlled instead of a valve plate in that every displacement room a check valve is assigned over which connects to high and low pressure. Independent of The direction of rotation will therefore be controlled via check valves Unit always out at volume increase suck the low pressure and volume reduction in the high pressure promote. As a motor, the pump P2 can not work. This direction independence comes in the present invention advantageous for carrying, because independently from lifting or lowering the lift cylinder the basic supply of the other Consumer Z1, Z2 is secured.

Farther is in the working line from the pump P1 to the lifting cylinder HZ Priority valve PRV provided that the inflowing from the first pump P1 volume flow as needed on the lifting cylinder HZ on the one hand and on the other Consumers Z1, Z2 on the other hand distributed, so that the pump P2 accordingly supports becomes. In the same way, this also happens in lowering, at the priority valve the now flowing back from the lifting cylinder HZ volume flow on the first pump P1 and as needed also on the other consumers Z1, Z2 distributed.

Between the priority valve PRV and the lifting cylinder HZ is provided a lift valve HV, as electrically controlled continuous valve is formed and between the limit positions "closed" and "fully open" is adjustable.

With the pressure difference occurring across the lift valve HV, the priority valve PRV is acted upon. If no additional consumers but only the lifting cylinder is to be operated, the lift valve HV opens completely, so that there is no Druckab case over the control edge there. The speed control of the lifting cylinder HZ then takes place via the rotational speed of the pump P1 and the priority valve PRV is not deflected from its central position, in which the connection to the lifting cylinder HZ fully open and the diversion is interrupted to the other consumers. In this situation, the pump also pumps P2, which rotates at the same speed. The excess volume flow is discharged via the pressure compensator DWP to the tank. This requires a certain loss of energy, but can be kept low if the pump P2 is correspondingly weak dimensioned.

If only the other consumers Z1, Z2 are actuated, the lift valve remains closed, creating a pressure before that, the priority valve pushes in the left position in the drawing. In this position the working line of the pump P1 via the check valve RÜV with that connected to the pump P2, so that the flow rate of the pump P1 is added to that of the pump P2. The other consumers Z1, Z2 are thus supplied as if by a single pump. After it while there is no excess flow, the over drain the pressure compensator DWP would have There are no inherent energy losses in this mode on.

If the lifting cylinder and other consumers are actuated simultaneously, then the lift valve is only partially opened so that its control edge a significant pressure drop occurs, the priority valve Move PRV to the right position in the drawing, in which the Pump P1 with both the lifting cylinder and the check valve RÜV with the additional Connected to consumers Z1, Z2 and so supports the pump P2.

The Working lines of the pumps P1 and P2 are in a known manner by pressure relief valves secured to the tank T out. Furthermore is for security reasons before the lifting cylinder HZ a load-holding valve LHV inserted, the a sagging of the load after completion of the lifting prevented or prevents the load from falling too fast.

The operation of the further consumers Z1, Z2 can be done in various ways. In the embodiment of 1 For this purpose, a so-called load-sensing system LSS is provided. The distribution of the volume flow to the individual consumers Z1, Z2 with their different pressure levels in a known manner with individual pressure compensators DW1, DW2 which the directional valves V1, V2 are connected downstream. The shuttle valve WV supplies the highest pressure to the input pressure compensator DWP, where this pressure is compared with the system pressure present in the working line of the pump P2.

• a) Heben, Hubzylinderdruck größer als bei den weiteren Verbrauchern: In diesem Fall wird der Differenzdruck am Prioritätsventil PRV und an den Individualdruckwaagen DW1, DW2 der weiteren Verbraucher Z1, Z2 weggedrosselt. Die entstehende Verlustleistung wächst mit der Geschwindigkeit dieser Verbraucher.
• b) Heben, Hubzylinderdruck kleiner als bei den weiteren Verbrauchern: In diesem Fall wird der Differenzdruck nur am Prioritätsventil PRV weggedrosselt. Die entstehende Verlustleistung wächst mit der Geschwindigkeit des Hubzylinders.
• c) Senken, Hubzylinderdruck größer als bei den weiteren Verbrauchern: In diesem Fall wird der Differenzdruck nur an den Individualdruckwaagen DW1, DW2 der weiteren Verbraucher Z1, Z2 weggedrosselt. Die entstehende Verlustleistung wächst mit der Geschwindigkeit dieser Verbraucher. Im Prioritätsventil findet kein Druckabfall statt.
• d) Senken, Hubzylinderdruck kleiner als bei den weiteren Verbrauchern: In diesem Fall öffnet das Rückschlagventil RÜV nicht. Die Geschwindigkeit des Hubzylinders ist durch die Drehzahl der Pumpe P1 eindeutig festgelegt. Für die weiteren Verbraucher kann dies eine Unterversorgung bedeuten, wenn die zweite Pumpe P2 so gering dimensioniert ist, dass sie auf die Mithilfe der ersten Pumpe P1 angewiesen ist. Aber auch dann ist die Funktion der Schaltung, nämlich der unabhängige Betrieb von Hubzylinder und weiteren Verbrauchern, trotz einer gewissen Komforteinbuße grundsätzlich noch gegeben.

In the operation of the hydraulic circuit according to the invention, the following four cases are to be distinguished:

• a) Lifting, lifting cylinder pressure greater than in the other consumers: In this case, the differential pressure at the priority valve PRV and at the individual pressure compensators DW1, DW2 of other consumers Z1, Z2 throttled away. The resulting power dissipation increases with the speed of these consumers.
• b) Lifting, lifting cylinder pressure smaller than with the other consumers: In this case, the differential pressure is restricted only at the priority valve PRV. The resulting power loss increases with the speed of the lifting cylinder.
• c) Lowering, lifting cylinder pressure greater than in the other consumers: In this case, the differential pressure is throttled away only at the individual pressure compensators DW1, DW2 the other consumer Z1, Z2. The resulting power dissipation increases with the speed of these consumers. There is no pressure drop in the priority valve.
• d) Lowering, lifting cylinder pressure smaller than for the other consumers: In this case, the check valve RÜV does not open. The speed of the lifting cylinder is clearly defined by the speed of the pump P1. For the other consumers, this may mean a shortage when the second pump P2 is dimensioned so small that it depends on the assistance of the first pump P1. But even then, the function of the circuit, namely the independent operation of lifting cylinder and other consumers, despite a certain loss of comfort in principle still exists.

In the latter case, in which only little energy is available anyway, it may be possible to dispense with the recovery in the lowering operation by the volume flow is discharged via a flow control valve. This possibility is in 2 shown. Apart from the load-lowering valve LSV and two pressure sensors D1, D2, this circuit is identical to that of FIG 1 , The reference numerals for the same circuit parts have been retained. The aforementioned operating state d), in which the lifting cylinder pressure is lower in the lowering operation than in the other consumers Z1, Z2, is detected with the pressure sensors D1, D2. If appropriate, the volume flow from the lifting cylinder to the tank T is discharged via the correspondingly controlled load-lowering valve LSV during lowering.

3 shows a further embodiment in which the additional consumers Z1, Z2 are supplied via a constant current system KSS. On the lift drive side, the circuit is identical to that of 1 , The other consumers Z1, Z2 are connected in series via the valves V1, V2 and are supplied by a volume flow independent of the level of the load pressure. Although such a constant current system does not offer the possibility of pressure and flow adjustment to the current requirements of the consumer, but is much simpler structure than that in the 1 and 2 illustrated load-sensing system. For the operation that applies to 1 Said in the same way. Similarly, the circuit for the low-load lowering operation can be extended with a flow control valve, as it is based on the 2 is described.

The proposed circuit with a motor double pump unit thus allows an efficient energy recovery from the potential energy of a lifting cylinder at the same time Operation of other consumers, in comparison with conventional Circuits of effort for the pumps and the valve technology is reduced.

D1, D2

pressure sensors

DPW

pressure compensator

DW1 / DW2

Individual pressure compensators

HV

globe valve

HZ

lifting cylinder

KSS

Constant current system

LHV

Load-holding valve

LSS

Load Sensing System

LSV

Lastsenkventil

MDP

Motor double pump unit

M / G

Motor / generator

P1, P2

pump

PRV

priority valve

RÜV

check valve

T

tank

V1 / V2

way valves

WV

shuttle valve

Z1 / Z2

working cylinder other consumers

Claims (11)

Hydraulic circuit arrangement with a first pump (P1) driven by an electric motor (M / G) and associated with a lifting cylinder (HZ), wherein the electric motor (M / G) as generator and the first pump (P1) can be operated as a hydraulic motor for energy recovery, in order to recover potential energy of the lifting cylinder (HZ), and with a second pump (P2) for supplying at least one further consumer, characterized in that - the electric motor (M / G), the first pump (P1) and the second pump (P2 ) are designed as a motor double pump unit (MDP), - wherein the first pump (P1) in the lowering operation of the lifting cylinder (HZ) as a hydraulic motor operates reversing the direction of rotation while the second pump (P2) always works as a pump with a constant conveying direction, and wherein - between the first pump (P1) and the lifting cylinder (HZ) a priority valve (PRV) is arranged, the flow of the first pump (P1) flowing as needed to the lifting cylinder (HZ) on the one hand and on the at least one other consumer on the other hand and in the lowering of the lifting cylinder (HZ) flowing back flow corresponding to the at least one consumer and the first pump (P1). Hydraulic circuit arrangement according to claim 1, in which in the working line of the first pump (P1) between the priority valve (PRV) and the lifting cylinder (Hz) an electrically controllable globe valve (HV) is arranged, the simultaneous operation of the lifting cylinder (HZ) and at least one other consumer partially opens and in its two limit positions on blocking and on passage the working line of the first pump (P1) switches, the lifting valve (HZ) fully opens, when only the lift cylinder (HZ) is operated alone. Hydraulic circuit arrangement according to claim 1 or 2, where the priority valve (PRV) from the over the pressure difference occurring in the lift valve (HV) is controlled. Hydraulic circuit arrangement according to claim 3, in which in a first extreme position of the priority valve (PRV) the first pump (P1) on the one hand via a throttle with the lifting valve (HV) and on the other hand with the at least one other consumer connected is. Hydraulic circuit arrangement according to claim 3 or 4, in which in a second extreme position of the priority valve (PRV) the working line coming from the first pump on passage switched and at the same time with the at least one other consumer connected is. Hydraulic circuit arrangement according to one of claims 3 to 5, wherein the priority valve (PRV) has a middle position in which the management of the first pump (P1) switched to passage and the line to the at least one other consumer is blocked. Hydraulic circuit arrangement according to one of claims 1 to 6, in which in the from the priority valve (PRV) to at least leading another consumer Line a check valve (RÜV) provided is that at overpressure in the leading from the first pump (P1) to the lifting cylinder (HZ) Work management opposite opens the pressure generated by the second pump (P2). Hydraulic circuit arrangement according to one of claims 1 to 7, wherein the at least one further consumer via a Load Sensing System (LSS) is supplied. Hydraulic circuit arrangement according to one of claims 1 to 7, wherein the at least one further consumer via a Constant current system (KSS) is supplied. Hydraulic circuit arrangement according to one of claims 1 to 9, in which an electrically controllable load-reducing valve (LSV) is provided, which in the lowering operation, the volume flow from the lifting cylinder without energy recovery to the tank (T) derived.  Hydraulic circuit arrangement according to claim 10, in which in the working lines of the first and the second Pump (P1, P2) each pressure sensors (D1, D2) for controlling the Load-lowering valve (LSV) are provided.