Patent Publication Number: US-2023133918-A1

Title: Hydropneumatic suspension system for vehicles

Description:
The invention relates to a hydropneumatic suspension system for vehicles, at least consisting of an axle suspension and a cabin suspension, which for supplying them with pressurized fluid can be connected to a pressure supply source. 
     An axle suspension device for vehicles, in which load conditions change, is known from DE 10 2004 040 636 A1. The device is equipped with: two suspension cylinders, each having pressure chambers; a load-sensing system for generating pressure; a supply line forming two main branches between these chambers and a pump port and a tank port and level control system. Two valves are installed in each main branch. One of the valves in the first main branch is a pressure control valve, via which the pressure setting for the respective predefinable pressure chamber of the respective suspension cylinder and the level control are achieved, for which purpose the pressure control valve can be actuated electrically by means of a control device. 
     A damping system in the form of a hydraulic cabin suspension is known from DE 10 2015 007 075 A1. The system is equipped with a hydraulically actuated differential cylinder that is deflected and rebounds, and with a hydraulic accumulator connected to the differential cylinder at the end of its piston chamber and rod chamber. The piston and rod chambers of the differential cylinder are interconnected via a proportional throttle valve and two check valves in such a way that, both when the cylinder piston is retracted and when it extends, essentially only the differential volume from the piston chamber and rod chamber is routed via the proportional throttle valve during operation of the system. In this way, proportional damping is provided for the respective differential cylinder. 
     In practice, such an axle suspension device and such a cabin suspension system are regularly used as hydropneumatic suspension systems for a vehicle, in that they are each installed at the vehicle in the form of a separately operating assembly having its own fluid supply and associated valve control, which necessitates the provision of suitable installation space on the vehicle. 
     The invention addresses the problem of improving the known hydropneumatic suspension system to be able to be operated in an installation-space-saving, energy-efficient manner and with high control dynamics. 
     This problem is solved by a hydropneumatic suspension system for vehicles, having the features of claim  1  in its entirety. 
     In accordance with the characterizing part of patent claim  1 , the hydropneumatic suspension system according to the invention is characterized in that a control device can be used to jointly to control both the axle suspension and the cabin suspension, and in that, based on a priority detection system including a sensor device for the respective suspension, the supply with pressurized fluid of the one suspension takes precedence depending on demand over the other suspension. 
     As a result—in contrast to the suspension system known from the prior art—the axle suspension and the cabin suspension are combined in a joint suspension concept. Depending on the sensor data acquired by the sensor device, the priority detection system, regularly implemented by a computer unit, determines, which of the two suspensions takes precedence over the other where the supply with fluid at a presettable pressure is concerned to ensure their function in an optimum manner. Due to the central priority detection system, which actuates the control device accordingly, significantly reduced control effort at reduced hydraulic drive power is required to actuate the two suspensions. In addition, by combining the suspension systems for the axle and the cabin in a joint, interconnected actuation concept, the amount of hydraulic piping required as part of the required interconnection, as well as the hydraulic pump capacity and the required volume of control valves, can be reduced, which helps to reduce the installation space required on the vehicle. 
     By reducing the number of parts for the hydropneumatic suspension system, the weight is also reduced and there is no undesirable overlap or interference due to the adjustment of the respective suspension, in particular because of level control, via the priority detection system. 
     In a preferred exemplary embodiment, provision is made for the control device to be formed from a single control block having at least one utility port each for the assigned suspension as well as a pressure supply port and a return port. This keeps the number of fluid lines to a minimum, which also reduces the assembly effort for the suspension system. 
     In a further preferred exemplary embodiment, provision is made for the respective suspension to have at least one hydraulic power cylinder with a piston rod unit, the position of which is monitored by means of the sensor device in the form of at least one displacement sensor. In contrast to hydraulic condition monitoring using pressure sensors, the displacement sensors are used to directly detect the extending and retraction behavior of the respective power cylinder, in which way conclusions can be drawn about the dynamics of the vehicle damping and suspension system as a whole. 
     In a further preferred exemplary embodiment provision is made for the fluid end of both the piston chamber and the rod chamber of a power cylinder to be connected to at least one hydraulic accumulator, the gas-end preload of which presets the spring/damper behavior for the respective power cylinder. Owing to the circuitry used, in which the hydraulic accumulators can react directly to changes in the piston-rod chamber of a power cylinder, a highly dynamic response of the suspension system as a whole is achieved. 
     In a further preferred exemplary embodiment, for actuating the control device for the power cylinders provision is made for the priority detection system to have a computer unit, which evaluates the sensor data from the sensor device, which preferably has, in addition to the displacement sensors, at least one pressure monitoring device for at least parts of the hydraulic supply circuit of the control device. As a result, by means of the displacement sensors or position sensors based on the pressure monitoring device the position monitoring of the power cylinders can be checked in a redundant manner. 
     In a further preferred exemplary embodiment provision is made for the control device to be provided with individual control valves, preferably 2/2-way valves, which are assigned to a respective power cylinder and supplied with pressure fluid from a central valve, preferably in the form of a 3/2-way valve. As a result, the suspension system can be manufactured easily and cost-effectively using standard components, and additionally, the fast-switching directional control valves mentioned further improve the overall dynamics of the suspension system. 
     In a further preferred exemplary embodiment provision is made for the power cylinders of the axle suspension to be permanently interconnected in a fluid-conveying manner both at the piston end and at the rod end, and for the power cylinders to be each connected to a control valve on both the piston end and the rod end for the supply and removal of fluid relating to the axle suspension. This reduces the number of connections required when using hydraulic lines. 
     In a further preferred exemplary embodiment provision is made for the cabin suspension to be supplied with fluid by means of a further control valve starting from the central valve or to be relieved of pressure in the direction of the return port. In this way, the individual directional valves or switching valves are used to achieve a switching logic for the suspension, subdivided into valve assemblies, which increases functional reliability. 
     In a further preferred exemplary embodiment provision is made for the pressure fluid supply of the respective power cylinder to occur after actuation of the assignable control valve using the pressure of the pressure supply source and, for discharging pressure fluid from the respective power cylinder, this occurs via an orifice or throttle in a delayed manner. Such an orifice or throttle, which can also be of adjustable design, can be used to appropriately throttle the return flow of working fluid from the cylinders in the direction of the tank, which also contributes to reducing the speed of retraction of the power cylinders during lowering operations as part of the level control. 
     In another preferred exemplary embodiment, the control block is additionally provided with a load sensing port leading to the inlet end of the control valves. If necessary, the load-sensing port mentioned can be used to control the pressure supply for the suspension system by actuating a swing pump, and/or the load-sensing port can be used to supply fluid to other hydraulic components depending on demand. 
    
    
     
       Below, a, hydropneumatic suspension system according to the invention will be explained in more detail with reference to the drawing. The single FIGURE shows the hydropneumatic suspension system according to the invention not to scale and in the manner of a hydraulic circuit diagram. 
     
    
    
     The single FIGURE shows a hydropneumatic suspension system for vehicles according to the invention. The suspension system has an axle suspension  10  and a cabin suspension  12 , which can be controlled in conjunction by means of a control device  14  of the suspension system. To supply pressure fluid to the axle suspension  10  and the cabin suspension  12 , the suspension system can be connected to a pressure supply source (not shown in the figures), wherein the supply of pressure fluid to the one suspension  10 ,  12  takes precedence over the respective other suspension  12 ,  10 , as controlled by means of a priority detection system  16 , which is part of the suspension system and including a sensor device  18  for the respective suspension  10 ,  12 . 
     The control device  14  is formed from only one single control block  20 . The control block  20  has a first utility port  22  and a second utility port  24 , to which the axle suspension  10  is connected, and a third utility port  26 , to which the cabin suspension  12  is connected. In addition, a pressure supply port P and a load sensing port LS, each for connection to the pressure supply source, and a return port T are provided on the control block  20 . 
     The axle suspension  10  and the cabin suspension  12  each have two hydraulic power cylinders  28 ,  30 . The travels of the two piston rod units  32 ,  34  of the power cylinders  28 ,  30  of the respective suspensions  10 ,  12  are jointly monitored by a respective displacement sensor  36 . It is also conceivable for the travel of each piston-rod unit  32 ,  34  of the power cylinders  28 ,  30  to be monitored by a respective displacement sensor module not shown in the figures, wherein the two displacement sensor modules in conjunction form the displacement sensor  36  of the respective suspension  10 , 12 . The displacement sensors  36  are part of the sensor device  18 , which is part of the suspension system. 
     Every power cylinder  28 ,  30  of the axle suspension  10  and the cabin suspension  12  has a piston chamber  38  and a rod chamber  40 . 
     The fluid end of one hydraulic accumulator  42  each is connected to the piston chamber  38  and to the rod chamber  40  of a power cylinder  28  of the axle suspension  10 , which hydraulic accumulators  42  specify the spring/damper behavior for this power cylinder  28 . The two piston chambers  38  of the power cylinders  28  of the axle suspension  10  are permanently interconnected in a fluid-conveying manner via a first fluid line  44 , and the two rod chambers  40  are interconnected via a second fluid line  46 . 
     The piston chamber  38  and the rod chamber  40  of each power cylinder  30  of the cabin suspension  12  are jointly connected to a respective associated hydraulic accumulator  42  via a 4/2-way proportional valve  48  each, wherein an adjustable closing force under electromagnetic control can be used to move the valve piston of the 4/2-way proportional valve from a first position shown in the FIGURE to a second position against the force of a compression spring. In this case, the rod chamber  40  of the respective power cylinder  30  is connected to a first port  48 . 1  of the respective proportional valve  48  and the piston chamber  38  of this power cylinder  30  is connected to a second port  48 . 2  of the respective proportional valve  48  in a fluid-conveying manner. Further, the respective proportional valve  48  has a third  48 . 3  port and a fourth  48 . 4  port, both of which are connected to a first branching point  50  and a second branching point  52 , respectively, in a fluid-conveying manner. The hydraulic accumulator  42  is connected to the respective branching point  50 ,  52 , as is the rod chamber  40  via a third fluid line  54  and the piston chamber  38  of the respective assigned power cylinder  30  via a fourth fluid line  56 . One check valve  58  each is provided in the third fluid line  54  and fourth fluid line  56 , which check valve  58  opens in the direction of the fluid flow of the respective power cylinder chambers  38 ,  40  against the force of a compression spring. The two branching points  50 ,  52  of the cabin suspension  12  are interconnected in a fluid-conveying manner via a fifth fluid line  60 . The gas-end preload of the respective hydraulic accumulator  42  determines the spring-damper behavior for the respective power cylinder  30  of the cabin suspension. 
     In the first end position of the valve piston of the respective proportional valve  48  of the cabin suspension  12  shown in Fig., the first port  48 . 1  is connected to the third port  48 . 3  and the second port  48 . 2  is connected to the fourth port  48 . 4  in a fluid-conveying manner via a fluid connection having one throttle each. In the second end position, the first port  48 . 1  is connected to the third port  48 . 3  in a fluid-conveying manner and the second port  48 . 2  is connected to the fourth port  48 . 4  in a fluid-conveying manner via respective fluid connections free of flow-constrictions. 
     The priority detection system  16  has a control unit in the form of a computer unit  62 , on which software for evaluating the sensor data of the sensor device  18  and for actuating the control device  14  based on the evaluated sensor data is installed. The sensing device  18  includes displacement sensors  36  and a pressure monitoring device  64  for detecting fluid pressure in a part of the hydraulic supply circuit of the control device  14 , each of which is connected to the computer unit  62  on the inlet end. 
     The control device  14 , which is a part of the priority detection system  16 , has a first control valve V 2  and a second control valve V 3  that supply pressurized fluid to the power cylinders  28  of the axle suspension  10 , and a third control valve V 4  that supplies pressurized fluid to the power cylinders  30  of the cabin suspension  12 . Every control valve V 2 , V 3 , V 4  is designed as a 2/2-way switching valve. In addition, the control device  14  has a central valve V 1  in the form of a 3/2-way switching valve that supplies pressurized fluid to every control valve V 2 , V 3 , V 4 . 
     The first port V 1 . 1  of the central valve V 1  is connected to the return port T of the control block  20  in a fluid-conveying manner and the third port V 1 . 3  of the central valve V 1  is connected to the pressure supply port P of the control block  20  via a sixth fluid line  74  in a fluid-conveying manner. 
     A second port V 1 . 2  of the central valve V 1  is connected to a third branch point  76  in a fluid-conveying manner, which is connected to a first port V 2 . 1 , V 3 . 1  of each of the first control valve V 2  and the second control valve V 3  and to a first port V 4 . 1  of the third control valve V 4  via a seventh fluid line  78 , each in a fluid-conveying manner. The third branch point  76  is also connected to the load sensing port LS of the control block  20  via an eighth fluid line  80  in a fluid-conveying manner. The valve piston of the central valve V 1  can be moved in an electromagnetically controlled manner from a first switching position shown in Fig. to a second switching position against the force of a compression spring. In the first switching position, the second port V 1 . 2  of the central valve V 1  is connected to its first port V 1 . 1  in a fluid-conveying manner and free of flow constrictions, wherein the third port V 1 . 3  of the central valve V 1  is disconnected. In the second switching position, the second port V 1 . 2  of the central valve V 1  is connected to the third port V 1 . 3  in a fluid-conveying manner, wherein the first port V 1 . 1  is disconnected. 
     The first control valve V 2  has its second port V 2 . 2  connected to a fourth branch point  82 , which is connected to the first utility port  22  of the control block  20  and to a control block port  84  for the pressure monitoring device  64  in a fluid-conveying manner. The first utility port  22  is connected to the second fluid line  46  of the axle suspension  10  in a fluid-conveying manner. The pressure monitoring device  64  as a pressure-to-current converter is connected to the port  84  for the pressure monitoring device  64 . The second port V 3 . 2  of the second control valve V 3  is connected to the second utility port  24  of the control block  20 , which is connected to the first fluid line  44  of the axle suspension  10  in a fluid-conveying manner. The second port V 4 . 2  of the third switching valve V 4  is connected to the third utility port  26  of the control block  20 , which is connected to the fifth fluid line  60  of the axle suspension  10  in a fluid-conveying manner. The valve pistons of the first switching valve V 2 , the second switching valve V 3  and the third switching valve V 4  can each be moved against the force of a compression spring in an electromagnetically controlled manner from a first switching position shown in the FIGURE to a second switching position. In the first switching position, the first port V 2 . 1 , V 3 . 1 , V 4 . 1  of the respective switching valve V 2 , V 3 , V 4  are separated from the second port V 2 . 2 , V 3 . 2 , V 4 . 2 , whereas in the second switching position, these ports are interconnected in a fluid-conveying manner without flow restriction. 
     The outlet end of the computer unit  62  is electrically connected to the central valve V 1 , the first V 2 , the second V 3  and the third V 4  control valve as well as the two proportional valves  48  of the cabin suspension  12  to individually actuate the respective valve Vito V 4 . 
     A first throttle BL 1  is provided in the sixth fluid line  74  between the pressure supply port P of the control block  20  and the third port V 1 . 3  of the central valve V 1 . A second throttle BL 2  is installed in the fluid line between the second port V 2 . 2  of the first control valve V 2  and the fourth branch point  82 , and a third throttle BL 3  is installed in the fluid line between the second port V 3 . 2  of the second control valve V 3  and the second utility port  24 . A fourth throttle BL 4  is provided in the seventh fluid line  78  between the third branch point  76  and the first port V 4 . 1  of the third control valve V 4 . A fifth throttle BL 5  is installed in the fluid line between the second port V 4 . 2  of the third control valve V 4  and the third utility port  26 . The respective second to fifth throttles BL 2  to BL 5  are used in particular to delay the discharge of pressure fluid from the respective power cylinders  28 ,  30 . 
     In parallel to the second throttle BL 2 , a check valve  58  is provided between the second port V 2 . 2  of the first control valve V 2  and the fourth branch point  82 , which check valve  58  opens in the direction of the fourth branch point  82  against the force of a compression spring. In parallel with the third throttle BL 3 , a check valve  58  is installed between the second port V 3 . 2  of the second control valve V 3  and the second utility port  24 , which check valve  58  opens in the direction of the second utility port  24  against the force of a compression spring. A check valve  58  is introduced into the eighth fluid line  80  between the third branch point  76  and the load-sensing port LS of the control block  20 , which check valve  58  opens in the direction of the load-sensing port LS against the force of a compression spring. 
     An adjustable pressure relief valve  88  is installed between the second utility port  24  and the return port T in a ninth fluid line  86 , wherein the inlet end of adjustable pressure relief valve  88  is connected to the second utility port  24  and the outlet end of said valve  88  is connected to the return port T in a fluid-conveying manner. 
     The operating principle of the suspension system according to the invention is explained in more detail below: 
     If the computer unit  62  determines, as a function of the measured values of at least one of the displacement sensors  36  and, if applicable, of the pressure monitoring device  64 , that the axle suspension  10  and/or the cabin suspension  12  require(s) pressure fluid, then the central valve V 1 , if this is not already in its second switching position, is activated by the computer unit  62  in such a way that the valve piston of the central valve V 1  moves into its second switching position. As a result, every control valve V 2 , V 3 , V 4  is supplied with pressurized fluid via the central valve V 1  and the third branch point  76 . 
     Depending on the demand for pressure fluid of the respective suspension  10 , 12 , the respective control valve V 2 , V 3 , V 4  is then controlled by the computer unit  62  in such a way that its valve piston moves from its first switching position to its second switching position, as a result of which the respective power cylinder  28 ,  30  of the respective suspension  10 ,  12  is supplied with pressure fluid. In this case, the supply of the suspension  10 , 12  having the greater demand for pressure fluid takes precedence. 
     If the first control valve V 2  is arranged in its second switching position, the rod chambers  40  of both power cylinders  28  of the axle suspension  10  are simultaneously supplied with pressurized fluid via the central valve V 1  and the first control valve V 2 , resulting in the piston rod units  32  of the power cylinders  28  retracting. At the same time, the fluid in the respective piston chambers  38  is at least partially displaced into the hydraulic accumulator  42  connected to the piston chambers  38 . If the second control valve V 3  is arranged in its second switching position, the piston chambers  38  of both power cylinders  28  of the axle suspension  10  are simultaneously supplied with pressurized fluid via the central valve V 1  and the second control valve V 3 , resulting in the piston rod units  32  of the power cylinders  28  extending. At the same time, the fluid in the respective rod chambers  40  is at least partially displaced into the hydraulic accumulator  42  connected to the rod chambers  40 . If the third control valve V 4  is arranged in its second switching position, the piston chambers  38  and the rod chambers  40  of both power cylinders  30  of the cabin suspension  12  are simultaneously supplied with pressurized fluid. 
     For the discharge of pressure fluid from the piston chambers  38  and/or the rod chambers  40  of the power cylinders  28 ,  30  of the respective suspension  10 , 12 , when the valve piston of the respective control valve V 2 , V 3 , V 4  is arranged in its second switching position, the central valve V 1  is actuated by means of the computer unit  62  in such a way that the valve piston of the central valve V 1  moves into the first switching position, in which the central valve V 1  connects the third branching point  76  to the return port T. 
     If the fluid pressure at the second utility port  24  exceeds a predeterminable threshold value, the pressure relief valve  88  is used to relieve this pressure towards the return port T via the ninth fluid line  86 .