Hydraulic circuit arrangement with recovery of energy

Abstract

The invention relates to a hydraulic circuit arrangement having a first pump which is driven by an electric motor and is assigned to a lifting cylinder, wherein, in order to recover energy, the electric motor can be operated as a generator and the first pump can be operated as a hydraulic motor in order to recover potential energy of the lifting cylinder, and having a second pump for supplying at least one further load. The electric motor, the first pump and the second pump are embodied as a motor/double pump assembly, wherein in the lowering mode of the lifting cylinder the first pump acts as a hydraulic motor with reversal of the rotational direction while the second pump always operates as a pump with a constant delivery direction. Arranged between the first pump and the lifting cylinder is a priority valve which, depending on requirements, distributes the volume flow which flows in from the first pump to the lifting cylinder on the one hand, and to the at least one further load on the other, and the volume flow which flows in from the lifting cylinder in the lowering mode accordingly to the at least one load and the first pump.

1 . Hydraulic circuit arrangement having a first pump (P 1 ) which is driven by an electric motor (M/G) and is assigned to a lifting cylinder (HZ), wherein, in order to recover energy, the electric motor (M/G) can be operated as a generator and the first pump (P 1 ) can be operated as a hydraulic motor in order to recover potential energy of the lifting cylinder (HZ), and having a second pump (P 2 ) for supplying at least one further load,
 characterized
 in that the electric motor (M/G), the first pump (P 1 ) and the second pump (P 2 ) are embodied as a motor/double pump assembly (MDP), 
 wherein in the lowering mode of the lifting cylinder (HZ) the first pump (P 1 ) acts as a hydraulic motor with reversal of the rotational direction while the second pump (P 2 ) always operates as a pump with a constant delivery direction, and wherein 
 arranged between the first pump (P 1 ) and the lifting cylinder (HZ) is a priority valve (PRV) which, depending on requirements, distributes the volume flow which flows in from the first pump (P 1 ) to the lifting cylinder (HZ) on the one hand, and to the at least one further load on the other, and the volume flow which flows in from the lifting cylinder (HZ) in the lowering mode accordingly to the at least one load and the first pump (P 1 ). 
   
   
   
       2 . Hydraulic circuit arrangement according to  claim 1 , in which arranged in the working line of the first pump (P 1 ) between the priority valve (PRV) and the lifting cylinder (HZ) is an electrically controllable lifting valve (HV) which is partially opened during simultaneous operation of the lifting cylinder (HZ) and of the at least one further load, and in its two limiting positions switches the working line of the first pump (P 1 ) to the closed and open positions, wherein the lifting valve (HZ) opens fully if only when the lifting cylinder (HZ) is activated alone. 
   
   
       3 . Hydraulic circuit arrangement according to  claim 1 , in which the priority valve (PRV) is controlled by the pressure difference which occurs across the lifting valve (HV). 
   
   
       4 . Hydraulic circuit arrangement according to  claim 3 , in which, in a first extreme position of the priority valve (PRV), the first pump (P 1 ) is connected, on the one hand, to the lifting valve (HV) via a throttle and, on the other hand, to the at least one further load. 
   
   
       5 . Hydraulic circuit arrangement according to  claim 3 , in which, in a second extreme position of the priority valve (PRV), the working line which comes from the first pump is switched to the open position and at the same time is connected to the at least one further load. 
   
   
       6 . Hydraulic circuit arrangement according to  claim 3 , in which the priority valve (PRV) has a central position in which the working line of the first pump (P 1 ) is switched to the open position and the line to the at least one further load is closed. 
   
   
       7 . Hydraulic circuit arrangement according to  claim 1 , in which provided in the line leading from the priority valve (PRV) to the at least one further load is a non-return valve (RÜV) which opens when there is excess pressure in the working line leading from the first pump (P 1 ) to the lifting cylinder (HZ) compared to the pressure generated by the second pump (P 2 ). 
   
   
       8 . Hydraulic circuit arrangement according to  claim 1 , in which the at least one further load is supplied by a load-sensing system (LSS). 
   
   
       9 . Hydraulic circuit arrangement according to  claim 1 , in which the at least one further load is supplied by a constant flow system (KSS). 
   
   
       10 . Hydraulic circuit arrangement according to  claim 1 , in which an electrically controllable load-lowering valve (LSV) is provided, and in the lowering mode said load-lowering valve (LSV) diverts the volume flow from the lifting cylinder to the reservoir (T) without the recovery of energy. 
   
   
       11 . Hydraulic circuit arrangement according to  claim 10 , in which pressure sensors (D 1 , D 2 ) for actuating the load-lowering valve (LSV) are respectively provided in the working lines of the first and second pumps (P 1 , P 2 ).