Abstract:
The invention relates to a drive wheel traction chain for a hybrid vehicle comprising a heat engine and a hydraulic traction machine powered by hydraulic accumulators forming two power units that can be used to drive the drive wheels of the vehicle. The invention further comprises a recharge module including electricity storage batteries connected to an electric machine which drives a hydraulic recharge machine that powers the hydraulic accumulators, and a means for controlling the recharge module connected to the means for controlling the power units of the vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present invention is the US national stage under 35 U.S.C. §371 of International Application No. PCT/FR2011/052049, which was filed on Sep. 7, 2011 and which claims the priority of application FR 1057413 filed on Sep. 16, 2010 the content of which (text, drawings and claims) is incorporated here by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention concerns a traction chain comprising a hydraulic power unit, for a hybrid vehicle, as well as a hybrid vehicle outfitted with such a traction chain. 
       BACKGROUND 
       [0003]    Hybrid vehicles generally have a heat engine constituting the main power unit of the vehicle, and a supplemental power unit utilizing energy that can be stockpiled, such as electric or hydraulic energy, to optimize the operation of the heat engine and reduce its consumption. 
         [0004]    One known type of hybrid vehicle, presented in particular by the document JP-8282324, uses a heat engine constituting the main power unit, and a hydraulic machine connected to the drive wheels of the vehicle, being able to operate as a pump to charge hydraulic pressure accumulators, or as a motor to deliver a mechanical power to these drive wheels by withdrawing energy from the accumulators. 
         [0005]    In this way, during the braking phases one can utilize the hydraulic machine as a pump to recharge the hydraulic accumulators, recovering the kinetic energy of the vehicle. One can also utilize the hydraulic machine as a motor by withdrawing pressurized fluid from the hydraulic accumulators, and furnishing a mechanical power that is added to the power delivered by the heat engine, for the traction of the vehicle. 
         [0006]    This utilization of stockpiled hydraulic energy makes it possible to optimize the operation of the heat engine and to reduce its consumption, as well as the polluting gas emissions. The stockpiling of hydraulic energy also makes it possible to drive in hydraulic mode alone or zero emission “ZEV” mode, the heat engine remaining halted with a vehicle not emitting any polluting gas. 
         [0007]    The problem that arises with this type of vehicle is that the quantity of energy stockpiled is limited by the capacity of the hydraulic accumulators, which do not provide a good ratio between the quantity of energy stockpiled and the mass of these accumulators. The mileage in zero emission mode is thus slight in relation to the payload of the vehicle. 
       SUMMARY 
       [0008]    The purpose of the present invention is in particular to avoid these drawbacks of the prior art, and to provide a solution allowing a hybrid vehicle to have a substantial energy stockpile in relation to the payload by utilizing the hydraulic energy to power this vehicle. 
         [0009]    For this, the present disclosure provides a traction chain for the drive wheels of a hybrid vehicle, comprising a heat engine as well as a hydraulic traction machine powered by hydraulic accumulators, constituting two power units making it possible to drive the drive wheels of the vehicle, and additionally it comprises a recharge module including electricity storage batteries connected to an electric machine, which drives a hydraulic recharge machine that powers the hydraulic accumulators, and a means for controlling this recharge module connected to the means for controlling the power units of the vehicle. 
         [0010]    One advantage of this traction chain is that the electricity storage batteries, having a better storage capacity as compared to hydraulic accumulators and for a given weight, can supply a larger quantity of energy, which boosts the travel range of the vehicle, especially when driving with the heat engine halted. 
         [0011]    The traction chain of the invention, furthermore, can have one or more of the following features, which can be combined with each other: 
         [0012]    Advantageously, the hydraulic traction machine has its two power supply channels connected to a high-pressure hydraulic accumulator and to a low-pressure hydraulic accumulator. 
         [0013]    Advantageously, the hydraulic recharge machine has its two power supply channels connected each to one of the high and low pressure hydraulic accumulators. 
         [0014]    According to one embodiment, the hydraulic recharge machine has a variable cubic capacity that is regulated by the means of controlling the recharge module. 
         [0015]    Advantageously, the recharge module has an electric valve which allows isolation of the hydraulic circuit of this module from the hydraulic circuit of the hydraulic traction machine. 
         [0016]    Advantageously, the recharge module constitutes an independent subassembly that is mounted in the traction chain. 
         [0017]    Another object of the invention is methods of operation of a traction chain having any one of the previous features, and comprising the following operating modes. 
         [0018]    A first operating mode allows recharging of the hydraulic accumulators, the vehicle being halted or in motion, by driving the hydraulic recharge machine used as a pump from the electric machine consuming an electric current delivered by the batteries. 
         [0019]    A second operating mode makes it possible to recharge the batteries by driving the electric machine, supplying an electric current to charge these batteries from the hydraulic recharge machine used as a motor, receiving energy from the hydraulic accumulators, which are themselves recharged by the hydraulic traction machine during the braking phases of the vehicle. 
         [0020]    A third operating mode is implemented when the recharge module is no longer in service, by closing the isolating electric valve. 
         [0021]    Moreover, the object of the invention is a hybrid vehicle having a traction chain comprising a heat engine and a hydraulic traction machine powered by hydraulic accumulators, constituting two power units making it possible to drive the drive wheels of this vehicle, this traction chain having any one of the preceding features. 
     
    
     
       DRAWINGS 
         [0022]    The invention will be better understood and other features and advantages will appear more clearly upon reading the following specification, given as an example and not limiting, with regard to the enclosed drawings. 
           [0023]      FIG. 1  is a diagram of a traction chain of a hybrid vehicle according to the invention, having a recharge module. 
           [0024]      FIG. 2  is a diagram of this recharge module in a first operating mode. 
           [0025]      FIG. 3  is a diagram of this recharge module in a second operating mode. 
           [0026]      FIG. 4  is a diagram of this recharge module in a third operating mode. 
       
    
    
     DETAILED DESCRIPTION 
       [0027]      FIG. 1  presents a traction chain  1  of an automobile, comprising a heat engine  2 , driving a mechanical transmission  4  connected to a differential  6 , transmitting and distributing the movement to two drive wheels  8  of an axle, which can be the front wheels, the rear wheels, or all the wheels of the vehicle. 
         [0028]    The mechanical transmission  4  has a hydraulic traction machine  22  which can work as a motor or as a hydraulic pressure generator, one fluid outlet channel being connected to a high-pressure hydraulic accumulator  10 , and the other to a low-pressure hydraulic accumulator  12 . The hydraulic traction machine  22  displaces the fluid toward the low  12  or high pressure  10  hydraulic accumulator to respectively work as a motor consuming the energy of the high-pressure accumulator  10  and furnish a mechanical power, or to work as a pump and recharge the high-pressure accumulator  10 . 
         [0029]    A shaft of the hydraulic traction machine  22  is connected to the mechanical transmission  4 , so as to be able to drive the drive wheels  8  of the vehicle. The heat engine  2  as well as the hydraulic traction machine  22  can be connected so that they form power units arranged in series, in parallel, in series and in parallel alternately, or in power branching, depending on the different known configurations for the arrangement of a traction chain  1  of a hybrid vehicle. 
         [0030]    As a variant, the heat engine  2  can drive the front wheels of the vehicle, and the hydraulic traction machine  22  the rear wheels. 
         [0031]    The traction chain  1  moreover contains a recharge module  14  of the hydraulic accumulators  10 ,  12 , able to furnish a hydraulic pressure in these accumulators  10 ,  12  to recharge them, or to consume the hydraulic pressure of these accumulators  10 ,  12 . 
         [0032]    The recharge module  14  contains a link  16  to the electrical control network of the vehicle, a connection  18  to the public current distribution network, and a current outlet  20  providing an alternating voltage of 220 V. 
         [0033]      FIG. 2  details the recharge module  14 , comprising electricity storage batteries  30 , which can contain, for example, electrochemical accumulators or high-capacity capacitors, which are connected to a power electronics  32 . 
         [0034]    The power electronics  32  transforms the current received from the batteries  30  to supply it to an electric machine  34 , and regulate the machine  34  when it is working as a motor. The power electronics  32  also transforms the current received from this electric machine  34  when it is working as a generator, to recharge the batteries  30 . 
         [0035]    For this and the following figures, the arrows connecting the batteries  30 , the power electronics  32  and the electric machine  34 , as well as those placed at the hydraulic circuit  10 ,  12 , represent the direction of energy transfer. 
         [0036]    The electric machine  34  has a shaft connected to a hydraulic recharge machine  36  able to work as a pump or as a hydraulic motor, having a fixed cubic capacity or a variable cubic capacity. 
         [0037]    The hydraulic recharge machine  36  having a variable cubic capacity is regulated by a control computer  42  of the recharge module  14 . Advantageously, the hydraulic recharge machine  36  with variable cubic capacity comprises axial pistons driven by a swash plate whose inclination is controllable to adjust this cubic capacity. 
         [0038]    The hydraulic recharge machine  36 , when working as a pump driven by the electric machine  34 , as shown in  FIG. 2 , receives the fluid from the low-pressure accumulator  12  and transfers it to the high-pressure hydraulic accumulator  10 , passing through an electric valve  38  which is open. In this case, there is a recharging of hydraulic energy in the high-pressure hydraulic accumulator  10  from the electric energy contained in the batteries  30 . 
         [0039]    The hydraulic circuit of the recharge module  14  furthermore contains a pressure limiter  40  arranged between the power supply channels of the hydraulic recharge machine  36 , which makes it possible to limit the pressure difference to a maximum value in order to ensure safety in case of an incident in the system. In particular, it makes it possible to limit the pressure in the event that the electric machine  34  continues to furnish a power with the electric valve  38  closed, or with the high-pressure accumulator  10  completely filled. 
         [0040]    The control computer  42  of the recharge module  14  exchanges information as to the status of the vehicle by the link  16  with the electric control network of the hybrid power units  2 ,  22 , in particular, to regulate the power electronics  32 , the variable cubic capacity of the hydraulic recharge machine  36 , and the electric valve  38 . 
         [0041]    The control computer  42  in particular exchanges information as to the level of energy contained in the hydraulic accumulators  10 ,  12  and in the batteries  30 , so as to optimize these levels and let the heat engine  2  operate in the best performance conditions. 
         [0042]    The connection  18  with the public current distribution network is connected to the power electronics  32  to receive energy from the public current distribution network when the vehicle is hooked up to public current distribution network while parked, and to transform the energy so as to recharge the batteries  30 . 
         [0043]    The current outlet  20 , on the contrary, receives electric current from the batteries  30 , which is transformed by the power electronics  32  into alternating current of 220 V, in order to operate the accessories plugged into the vehicle. 
         [0044]    The operating mode of  FIG. 2  provides for recharging of the hydraulic accumulators  10 ,  12  when the vehicle is halted or in motion from electric current furnished by the batteries  30 . It will be noted that the batteries  30  having a higher energy level for a given weight than that of hydraulic accumulators  10 ,  12 , the travel range of the vehicle in zero emission mode is greater than that of a hybrid vehicle without a recharge module  14 . 
         [0045]    The operating mode of  FIG. 3  provides receipt of the the hydraulic energy coming from the operation of the transmission  4 , the high-pressure accumulator  10  furnishing a fluid in the hydraulic recharge machine  36  operating as a hydraulic motor, passing through the electric valve  38  which is open, to drive the electric machine  34  working as a generator, and to recharge the batteries  30 . 
         [0046]    In particular, the kinetic energy coming from the braking of the vehicle can be recovered, during a slowdown of this vehicle or during the descent of a slope, which is converted into hydraulic energy by the hydraulic traction machine  22 , then into electric energy by the hydraulic recharge machine  36  used as a motor to drive the electric machine  34 , which produces current stockpiled in the batteries  30 . 
         [0047]    In the same way, the quantity of energy stockpiled in the batteries  30  is greater than that in hydraulic accumulators  10 ,  12  of equivalent weight, which allows a greater recovery of energy. 
         [0048]    The operating mode of  FIG. 4  is used when the recharge module  14  is no longer in service, especially when the charge of the batteries  30  no longer allows for the exchange of energy with the hydraulic accumulators  10 ,  12 . 
         [0049]    In this case, the control computer  42  of the recharge module  14  closes the electric valve  38  to isolate the hydraulic circuit of this module and prevent a leakage flow in the hydraulic recharge machine  36  so as not to cause a loss of energy stored in the hydraulic accumulators  10 ,  12 . 
         [0050]    It will be noted that the recharge module  14  can constitute an independent subassembly, which is mounted on a hybrid vehicle comprising a transmission  4  having a hydraulic traction machine  22 , to boost the travel range of this vehicle when driving without polluting gas. In this way, the recharge module  14  can constitute a subassembly that is easily installed on the vehicle by connecting the hydraulic channels and the electrical connections.