Abstract:
A hydraulic module designed to be mounted on a hydraulic hybrid vehicle, characterised in that it forms a rigid and compact assembly comprising a body ( 32 ) receiving the high- and low-pressure accumulators intended to supply traction motors of the vehicle, comprising a generally parallelepipedal shape, and having attachment means designed to be fixed under a floor at the rear of the vehicle.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is the US National Stage under 35 US §371 of PCT/FR2013/053149 filed Dec. 18, 2013, which in turn claims priority to French application 1350109 filed on Jan. 7, 2013, the content of which (text, drawings and claims) is incorporated herein by reference. 
     BACKGROUND 
     The present invention relates to a module comprising high and low pressure hydraulic accumulators for a hybrid vehicle, and a hybrid vehicle comprising such module. 
     Certain hybrid vehicles have an internal combustion engine which drives a hydraulic pump to recharge accumulators with pressurized fluid in order to store energy, and hydraulic motors supplied by these accumulators driving the traction wheels of the vehicle. These vehicles also comprise a hydraulic pump connected to the traction wheels, in order to recuperate the kinetic energy of the vehicle during braking and to recharge the accumulators. 
     The hydraulic accumulators may comprise in particular a high pressure accumulator receiving pressure from the hydraulic pumps in order to supply the motors, and a low pressure accumulator receiving the fluid returning from these motors. 
     These hybrid vehicles optimize the operation of the combustion engine by reducing its fuel consumption and emissions of polluting gas. With the stored hydraulic energy, the vehicle can drive in strictly hydraulic mode called “ZEV”, without emission of polluting gas, while the combustion engine is stopped. 
     A known type of hydraulic motor, specifically disclosed in document FR-A1-2972682, comprises a rigid assembly containing the pressure accumulators, the hydraulic command block and the hydraulic traction motors, which are all mounted together. 
     A particular configuration presented in the document comprises traction motors installed on the front axle, which are mounted to the hydraulic command block and a first reservoir installed longitudinally under the vehicle, while the second reservoir is mounted transversally behind the first reservoir. 
     One problem posed by this particular configuration is that the rigid assembly is not easily adaptable to a hybrid vehicle with a combustion engine in front and a fuel tank installed under the rear passenger seats, which is the conventional platform of a vehicle with a combustion engine only. 
     In particular, the front part comprising the hydraulic command blocks and the first reservoir installed longitudinally under the vehicle requires significant modification of the platform of this vehicle, and takes up part of the space reserved for the fuel tank, significantly reducing its capacity. 
     In addition, this rigid assembly extending over most of the length of the vehicle poses important problems of passenger safety, in particular in case of a frontal or lateral collision at high vehicle speed. 
     SUMMARY 
     The goal of the present invention is to eliminate these disadvantages of prior art. 
     To this end, a hydraulic module is provided which is intended to be mounted on a hydraulic hybrid vehicle, characterized in that it forms a rigid and compact assembly comprising a generally parallelepipedal shaped body receiving the high and low pressure accumulators for supplying the traction motors of the vehicle, and provided with mounting means for underfloor mounting in the rear of the vehicle. 
     One advantage of the hydraulic module is that it can be installed flat under the rear trunk of the vehicle, while preserving the majority of the floor of a conventional vehicle in front of the rear axle, including the fuel tank which is not modified, in order to obtain significant standardization for the different types of vehicles built on the same platform. 
     The hydraulic module may comprise in addition one or more of the following characteristics, which may be combined. 
     Advantageously, the hydraulic module body comprises cylindrical bores, forming a support for the pressure accumulators. 
     Advantageously, the hydraulic module comprises transversally mounted cylindrical reservoirs. 
     In particular, the hydraulic module can comprise a high pressure accumulator and a low pressure accumulator juxtaposed one behind the other. 
     Advantageously, the hydraulic module comprises lids arranged on the lateral sides, covering the extremities of the hydraulic accumulators. 
     Advantageously, the hydraulic module comprises supports along its periphery, forming substantially horizontal planes, intended for mounting under the floor of the vehicle. 
     Advantageously, each support comprises elastic means for mounting to the floor of the vehicle. 
     Advantageously, the hydraulic module comprises a hydraulic command block integrated in this module. 
     The goal of the invention is also a hybrid vehicle comprising high and low pressure accumulators connected to hydraulic motors and pumps, whereby these accumulators are integrated in a hydraulic module comprising any one of the preceding characteristics. 
     In particular, the vehicle may comprise an “H” rear axle comprising a crossbeam attached at its ends to longitudinal suspension arms, while the module is mounted flat under the trunk of the vehicle, just behind the crossbeam. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       The invention will be better understood and other characteristics and advantages will be made clear in the following description provided as an illustrative example, with reference to the attached drawings in which: 
         FIG. 1  is a diagram presenting in top view a hybrid vehicle comprising different hydraulic elements arranged in known manner; 
         FIG. 2  is a perspective view of a hydraulic module according to the invention; 
         FIG. 3  is a bottom view of the rear end of a hybrid vehicle comprising this module, and 
         FIG. 4  is a schematic drawing of the hydraulic module. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a hybrid vehicle comprising a combustion engine  2  connected directly to a first hydraulic pump  4 , which receives supply fluid through a low pressure circuit  16 , and returns it at high pressure to a high pressure circuit  6 . 
     The low pressure circuit  16  and the high pressure circuit  6  are connected to a hydraulic command block  8 , which controls the hydraulic motor  18  and a second hydraulic pump  26 . 
     The hydraulic command block  8  is mounted in front of the long high pressure accumulator  10 , installed longitudinally under the floor of the vehicle. A low pressure accumulator  14  extending in a lateral direction, and disconnected from the high pressure reservoir, is installed under the vehicle behind the high pressure reservoir. 
     The hydraulic command block  8  is directly connected via an internal high pressure line to the high pressure accumulator  10 , and via an external low pressure line  12  to the low pressure accumulator  14 . 
     A transmission  20  with various gear ratios, supports on one side the hydraulic motor  18  which transmits mechanical power to the front traction wheels  24  via the wheel drive shafts  22 , while drawing energy from the high pressure accumulator  10 , and on the other side the second hydraulic pump  26  which receives mechanical power from the traction wheels, to recharge the accumulators. 
     This arrangement of the two pressure accumulators  10 ,  14  is relatively bulky and is not suitable for a high level of standardization between the different types of hybrid vehicles, or non-hybrid vehicles, using the same platform. 
     Furthermore, since each accumulator  10 ,  14  is independently mounted under the vehicle, it requires proper elastic fasteners to filter the vibrations. A certain number of hydraulic lines must be provided to connect the different hydraulic components, requiring mounting brackets and couplings involving risk of vibrations, leaks and rupture through material fatigue. 
     In addition, assembling and connecting these different elements under the floor of the vehicle is a relatively time consuming and complex operation. 
       FIG. 2  shows a top view of a hydraulic module  30 , with, as seen from above, a generally parallelepipedal shaped main body  32 , with the rectangular shape extending in a transverse direction, and a height which is small compared to the dimensions of the rectangular shape. 
     The main body  32  comprises two cylindrical passages  34 ,  36  of constant cross-section arranged transversally and juxtaposed one behind the other, which take up most of the volume of the body. Advantageously, the body  32  is made of a light material, such as an aluminum alloy or plastic material, which for instance can be molded or extruded to form a continuous profile. 
     Each cylindrical passage  34 ,  36  is prepared to accommodate a high or low pressure accumulator  35 ,  37 , comprising a cylindrical part which fits in the passage, and two pressure resistant dome shaped lids closing the extremities. 
     A hydraulic command block  39  is integrated in one side of the module  30 , and directly connected to the accumulators via short pressure lines  41 , with a much simplified system of connections with improved reliability, reduced weight and lower cost. 
     The rear hydraulic accumulator comprises external hydraulic couplings  38  mounted in the back of the main body  32 , and directly coupled to the accumulator. The couplings are connected to pressure lines starting in the front of the vehicle. Since these external couplings  38  are not located on a lateral side of the module  30 , the width of the module is reduced. 
     Each lateral side of the hydraulic module  30  is closed by a protective lid  40 , covering the extremities of the hydraulic accumulators, the hydraulic block and the internal couplings, in order to protect them from splashing water in particular. Note that the protective lid in the front of the figure is not shown. 
     The hydraulic module  30  comprises also fastening means, not shown in the figure, in order to mount it directly under the floor of the vehicle. 
       FIG. 3  shows the rear part of the vehicle comprising a substantially flat floor  50  which terminates in a rear vertical edge  52  separating it from a second upper part  54  at greater height. 
     A fuel tank  56  fills the space below the upper part of the floor  54 , and lies longitudinally between the vertical edge  52  and the crossbeam  58  of the rear axle supporting the rear wheels  62 . 
     The rear axle called an “H” axle, comprises the crossbeam  58  with each of its ends rigidly mounted to the central part of a longitudinal suspension arm  60 . The front part of these arms is connected by means of joint to the body of the vehicle, while the rear extremity is supporting a wheel  62 . This type of rear axle is easy to fabricate, and frees up substantial space behind the crossbeam  58 , between the suspension arms. 
     The fuel tank  56  and the rear axle are similar to those of conventional vehicles equipped with a combustion engine only. 
     The body of the vehicle comprises two longitudinal side members  64  installed on both sides under the trunk, above the suspension arms  60 . A crossmember  66  mounted to the rear end of the side members  64 , supporting the not shown rear bumper, is offset towards the rear relative to the body of the vehicle in order to create free space for deformation in case of a rear end collision. 
     The hydraulic module  30  is mounted flat under the trunk of the vehicle, by means of supports  70  arranged along its periphery, in particular at each corner of the module, forming a horizontal plane comprising each with a hole in which an elastic fastener is placed in order to filter vibrations. The installation of the module  30  under the body of the vehicle is easy and fast by feeding this module vertically under the trunk while engaging the elastic fasteners in the holes, and then tightening the fasteners. 
     The high and low pressure lines  72  coming from the front of the vehicle and mounted under the floor, are then coupled to the hydraulic module  30 . 
     The hydraulic module  30 , including the two accumulators and the hydraulic body, requires only a limited number of elastic fasteners to hold these elements under the vehicle, which ensures good acoustic performance, simplifies the assembly and reduces cost. 
     In addition, the two accumulators can be placed close together in the hydraulic module  30 , because they require no space between them, which is necessary when these two elements are mounted independently from each other by means of their own elastic fasteners, in order to provide relative movement between them. 
     The hydraulic module  30  with its generally parallelepipedal shape substantially fills all of the space below the floor of the trunk, longitudinally between the crossbeam  58  of the rear axle and the rear part of the body of the vehicle, and laterally between the two suspension arms  60 . In this way, by raising the height of the trunk floor, which is a small modification of the platform of conventional vehicles, the volumes under the body are optimized and completely filled. 
     Alternatively, the hydraulic module  30  can comprise more than two independent low and high pressure hydraulic accumulators, connected with each other directly inside this module by internal pressure lines. 
     The hydraulic module  30  according to the invention reduces the mass of hydraulic hybrid vehicles and simplifies the design as well as the assembly operations on the assembly line of the manufacturer, it also facilitates after sales service by providing quick exchange of the whole unit.