DE4038553C1 - Vehicle hydropneumatic suspension system - incorporates oil pump rod and air cushion control valve - Google Patents

Abstract

The hydropneumatic suspension legs take wheel load by projecting piston rods joined to a leakproof piston sepg. oil spaces in a cylinder so as to determine the length of the leg required. The bottom space oil is loaded by a primary gas cushion and the top space oil by a secondary gas cushion. A pump transfers oil between the spaces and a valve tripped at preset leg length returns the oil from one space to the other. A pump rod fixed in the cylinder base pumps oil in the hollow piston rod from top to bottom space until oil flows back through a return port controlled by the piston edge at preset pump length, using gas or oil sources to regulate primary cushion pressure. When ideal pressure is overshot as sensed (70) in the secondary cushion (47), control slide (21) should connect the primary cushion (7) to the gas source bleed line (12), or if pressure is undershot the slide connects the cushion to the feed line (13) so cushion pressure adapts to wheel load and the pump length determines the level of the vehicle. USE/ADVANTAGE - Motor vehicles. Gas cushion pressures in suspension are adapted to wheel load, depending on soft or hard selected suspension setting.

Description

The invention relates to a hydropneumatic suspension for a vehicle according to the preamble of patent claim 1.

From the German patent DE-PS 36 04 068, Fig. 5 is one Suspension of this type with a piston as a partition known between oil and gas, with the individual struts assigned position control elements are present, which the location of the Detect the separating piston in relation to a target position and at If there is a deviation from the target position, feed or release gas into the primary cushion. If with such a suspension from the patent DE-PS 11 35 779 Fig. 2, known and tried in practice compact spring legs should be used in which the partition between oil and gas as an elastic hose in one work cylinder surrounding annular space is formed and at that Deformation assumes an undefined position, it is not possible to record the position of the partition and for control processes to use.

The invention is concerned with the task of regulating other kind of feeding or draining, the formation of the partition as an elastic hose allowed.

This task is by the in the characterizing part of the patent claims 1 and 2 mentioned features solved and on this Way set a control point at which the spring detection with a required wheel load, clearly through the status changes change in pressure and volume in the two gas cushions is determined.

At the control point, the target pressure is the pressure in the secondary cushion, and its volume is obtained with the respective tempera from the amount of gas filled. This volume determines with gas-side control, the volume of the primary cushion in the Subtract the control point as the residual volume from the volume of the housing Lich volume of the secondary cushion and constant oil volume.

In the case of oil-side control, determine that of the pending one Wheel load derived pressure of the primary cushion and the on  the amount of gas filled the volume of the secondary poster at the control point.

The known from the German patent DE-PS 12 61 409 Suspension according to the preamble of claim 1, in which the pressure in the cover-side oil volumes of all struts by oil-side Control equipment is kept at the same level during the Pressure in the bottom oil volumes of the load Level control by means of separate level control or by self-pumping struts, could not teach be for the invention in which the pressure of the secondary cushion only indirectly by adjusting the pressure in the primary cushion to the required wheel load due to the displacement of the piston Oil is affected.

The target pressure can be arbitrarily adjustable and therefore a harder at a higher set pressure and a harder one at a lower one Target pressure a softer spring detection can be realized, such as is described below. By specifying one accordingly high or low set pressure can also raise or lower of the vehicle at a standstill.

Dynamic driving conditions subject to the mass force, for example, when cornering, there is an erection of the Vehicle instead of pumping up the spring struts and spring-loaded struts by the function of reflux sink opening.

With gas-side control - claim 1 - the drain lines can several Struts open into the inlet chamber of a gas compressor and the feed lines from the discharge chamber of the compression ters go out, so that the compressor directly gas out in spring struts for immediate compensation promotes the inclination of the vehicle during dynamic driving movements, as per itself from the German patent DE-PS 36 04 068 is known. This inclination compensation can correspond to a appropriate dimensioning of the compressor output can be carried out so quickly, that there is practically no inclination of the vehicle and that in The erection described above and the associated Oil transport between the lid-side and bottom-side oil volume does not take place or only takes place to a small extent.  

The gas compressor can also be used for static level control be used when a low pressure gas storage is arbitrary can be switched off to the inlet chamber or a high-pressure gas tank cher arbitrarily switched off connected to the outlet chamber are so that the static when the gas storage is switched on Level control takes place, as also from the last mentioned Patent specification is known.

With oil-side control - claim 2 - can in the same way as in the penultimate ten paragraph described, an inclination compensation with dynamic Movements take place when the drain and feeder are analogous connections for oil can be connected to an oil pump.

An adjustment of the vehicle level is possible by for required positions of the piston further reflux openings are arranged, of which the respectively not required with are provided with a locking device.

If after the level control has ended, the self-pumping function of the Shocks are undesirable, this is by blocking the backflow The pump valves can be opened and kept open.

By a desired length of the shock absorber, especially at the start a position sensor can be provided, together with or independently of the pressure sensor regulates the length by feeding or discharging gas or oil.

In the following description of an embodiment of the Invention is referred to the drawing. It shows

Fig. 1 shows a strut in section, with a feed line and a discharge line for gas,

Fig. 2 is a diagram of spring forces, which are pad by a secondary and a primary cushion generated in response to the hub,

Fig. 3 shows a spring characteristic at the same wheel load and different current setpoint pressures,

Fig. 4 spring identifiers at different wheel loads and the same nominal pressure,

Fig. 5 is a diagram for explaining control processes.

Occurs when the strut of FIG. 1 a with a mounting pin 15 provided the piston rod 52 by a seal 8 sealed from the cover 9 of an oil-filled working cylinder 2 of which is terminated by a provided with a fastening pin 14 base 19. A guided in the working cylinder 2 and sealed by a sealing ring 42 piston 4 at the end of the piston rod 52 separates the working cylinder 2 into a bottom-side working space 3 , from which the piston 4 via damping openings 54 in an intermediate wall 50 oil in a bottom space 64 against the Pressure of a primary cushion 7 displaced, and a cover-side working space 28 , from which the annular surface 59 of the piston 4 displaces oil against the pressure of a secondary cushion 47 , the amount of gas is constant.

A bottom-side annular space 66 and a lid-side annular space 46 are formed between the working cylinder 2 and a housing jacket 20 , separated by a transverse wall 60 . A tubular membrane 62 is clamped in the annular space 66 between the base 19 and the transverse wall 60 , which separates the gas of the primary cushion 7 from the base-side oil volume, which fills the residual space 68 of the annular space 66 , connecting bores 63 , the base space 64 and the base-side working space 3 , while in the annular space 46 the secondary cushion 47 is separated by a free oil level 49 from the cover-side oil volume, which fills the remaining space 48 of the annular space 46 , connecting bores 23 and the cover-side working space 28 .

The oil volumes are free of gas bubbles that free gas dissolved in the oil volume on the bottom side of higher pressure and in the cover side oil volumes lower pressure due to degassing will be divorced.

The hollow piston rod 52 forms a pump chamber 43 , into which a pump rod 51 , which is fastened by a ball joint 58 to the intermediate wall 50 and sealed by a seal 29, penetrates. The pump chamber 43 is connected to the working chamber 28 on the cover side by a suction valve 44 and to the working chamber 3 on the bottom side by a pressure valve 45 and also to the annular chamber 46 by a return opening 31 in the working cylinder 2 controlled by the piston 4 in the area of the sealing ring 42 . Below the same is a closed by a lock 33 reflux opening 32nd

A pressure sensor 70 is connected to the secondary cushion and connected through a control line 71 to a control unit 72 , which has a gas connection 73 to the primary cushion 7 and controls a control element in the form of a control slide 21 such that an open cushion 47 is exceeded when a setpoint pressure is exceeded Connection of the primary cushion 7 with a drain line 12 and when falling below the target pressure, a connection of the primary cushion 7 with a feed line 13 is made forth, check valves 75 and 76 a gas flow from the drain line 12 into the primary cushion 7 and a gas flow from this into the feed line 13 prevent.

Speed-dependent damping forces can be varied by dimensioning the damping bores 54 or by special damping valves. Load-dependent damping forces are given by the pumping work of the pump rod 51 and can be changed by the strength of the pump rod 51 or by throttle resistances of the suction and pressure valves 44 and 45 .

The shock absorber of FIG. 1 is equipped for a gas-side control. While the control unit 72 is retained, this shock absorber can also be used for an oil-side control if the gas connection 73 is replaced by an oil connection which leads from the bottom-side oil volume into the control unit at a suitable point, and the drain line and feed line are connected to an oil source.

In the case of level-regulating vehicle suspensions, spring identifications are used with spring rates proportional to the load in a large one Load range desired. This is too with gas-side regulation expect. To cheap spring in the suspension according to the invention to be able to prove identifications for an oil-side control, is an oil-side control in the following description provided the amount of gas in the primary cushion, such as mentioned at the beginning is constant.

The force exerted by the primary cushion on the bottom of the piston, Called primary force, is a compressive force on the piston rod, exerted by the secondary cushion on the ring surface of the piston te force, called secondary force, is a tensile force. The strut  carries a wheel load equal to the primary force minus the second intestinal strength.

In the diagram of Fig. 2 are leg lengths on the abscissa, on the ordinate primary forces upwards and secondary forces downwards. A secondary force line 80 is derived from an isothermal change in state of the amount of gas filled in the secondary cushion. A pump length 81 and a target force 82 , which is exerted by a first target pressure, define a first control point 83 , a pump length 84 and a target force 85 a second control point 86 .

By the control point 83 is a hatched from the bottom left to the top right operating section 91 with a compression range from the pump length 81 to a pressure stop 87 and a Ausfe der range from the pump length 81 to a train stop 88 selected by the control point 86 an opposite hatching ter operating section 92 , in which the desired pressure is lower than in section 91 with a pump length 84 , a pressure stop 89 and a train stop 90 .

In section 91 , a required wheel load 93 is kept in balance by a primary force 94 and in section 92 by a primary force 95 . The primary force lines 96 and 97 in sections 91 and 92 are derived from an isothermal change in the state of the amount of gas filled into the primary cushion.

By substitution of the primary force lines 96 and 97 with the associated parts of the secondary force line 80 , the spring identifiers 98 and 99 in Fig. 3 for the wheel load 93 with a compression range from the pump length 100 to the pressure stop 101 and a spring range from the pump length 100 to Train stop 102 . It can be seen that a softer spring identification 99 or a harder spring identification 98 can be set by changing the target pressure.

If are required at the target pressure 82 of the section 91 in FIG. 2 under schiedliche wheel loads 410, 411, 412, 413 of FIG. 4, formed during fed off oil source the spring identifiers 403, 404, 405 and 406 for these wheel loads with a stroke range from the tension stop 402 over the pump length 400 to the pressure stop 401 .

The spring identifiers according to FIG. 4 for different wheel loads indicate that spring load rates with an increase in wheel load of 1: 2.5, as shown, or more can be achieved by the invention, almost load proportional. because even with wheel loads under the wheel load 410 or over the wheel load 413 there are, as not shown, spring identifications with spring rates which are almost proportional to the load.

In the following explanation of control processes mean "regulating driving state" and "regulating standstill" that the External regulation when the vehicle is moving or stationary is switched on while "driving status" and "standstill" absolutely require a switched off external regulation. The pumping and backflow of oil within the shock absorber are called "internal regulation".

The respective volume of the secondary cushion depends on how Much oil contains the oil volume on the cover side. If this through internal regulation becomes smaller, the volume of Se increases cushions and drops its pressure when it through internal re volume increases, the volume of the secondary decreases cushions and increases his pressure.

The lid-side oil volume is not due to external regulation changeable, only the bottom oil volume. If this becomes greater through internal or external regulation the volume of the primary cushion increases and its pressure rises. If it gets smaller by internal or external regulation, the volume of the primary cushion increases and falls Print.

Below the abscissa of FIG. 5, the target force 582 , the control point 583 , the secondary force line 580 of FIG. 2 are taken over and a force line 510 with a larger volume of the secondary cushion and force lines 511 , 512 , 513 with a smaller volume are shown in dashed lines. Above the abscissa, a required wheel load 693 and force lines 610 , 680 , 611 , 612 , 613 of the primary forces are drawn, which together with the secondary forces on the force lines 500 , 580 , 511 , 512 , 513 of the wheel load 693 keep the balance.

In a first rule example, pump length 600 and setpoint force 582 may be present at a standstill and a wheel load 620 , to which spring identification 621 belongs, may be carried by the suspension strut. In the case of a wheel load 693 required by vehicle loading, the shock absorber springs up to a length of 624 , where the wheel load 693 is reached at point 622 . The associated secondary force 523 is now smaller than the target force 582 . When changing to regulating standstill, oil is fed in at the bottom and the spring strut cushions up to the pump length 600 , the primary forces along the force line 680 and the secondary forces along the force line 580 increasing until the desired force 582 is reached and oil stops feeding. Control point 583 is now defined for the following driving state. If the load is in the regular standstill, control point 583 is reached without the spring strut compressing up to length 624 , since the oil supply starts immediately.

For a second example with a smaller oil volume on the cover side than in the control point 583 , the secondary force 533 and the primary force 633 on the force lines 510 and 610, respectively, with a length of 634, were the starting points for regulation in the regulating standstill. By external control, the shock absorber rebounds until the pump length 600 is reached in point 535 , then the cover-side oil volume is increased by internal control and control point 583 is reached by further feeding in oil on the bottom side.

For a third example with a larger oil volume on the cover side than in the control point 583 , the secondary force 543 and the primary force 643 on the force lines 511 and 611 for a length of 644 are starting points for regulation in the regulating standstill, the secondary force 543 being smaller than the target force 582 . By external control, the shock absorber rebounds until the secondary force is equal to the desired force 582 at point 545 , and afterwards the control point 583 is reached in the regulating driving state by a succession of internal and external control, as indicated by the saw line 546 .

For a fourth example with a larger oil volume on the cover side than in the control point 583 , the secondary force 553 and the primary force 653 on the force lines 511 and 611 for a length of 654 are starting points for regulation in the regulating standstill, the secondary force 553 being greater than the target force 582 . By external control, the shock absorber springs in until the secondary force is equal to the target force 582 in point 545 , and thereafter the control point 583 along the saw line 546 is reached in the regulating driving state, as in the third example. One way to avoid deflection up to point 545 is that the target force 582 is converted to a target force 592 that is greater than the secondary force 553 , and the new control point 593 as in the second example, the control point 583 is reached. Since the target force 592 is now delayed to the target force 582 in the regulating driving state, the regulating point 583 can be achieved in the regulating driving state by the interaction of internal and external regulation, as indicated by the saw line 547 .

As a fifth example, another control option is described when the secondary force 563 exceeds the target force 582 . It consists in the arrangement of a separate Regelein direction, which in the spring deflection area from the pressure stop 601 to a control length 603 defined by a position sensor connects the bottom oil volume to the feed line of the oil source and removes the connection to the drain line as long as the pressure sensor in it Area reports that the target pressure has been exceeded. Thus, to feed the control length 603 in point 565 and then in the regulating driving state by the interaction of internal and external control, the desired force in point 566 and the control point 583 are reached, as the saw line 548 indicates.

For a sixth example, a secondary force 573 , which exceeds the desired force 582 at the pump length 600 , and the associated primary force 673 are starting points for regulation in the regulating driving state. External control drains oil on the bottom side until the control length 603 is reached at point 575 on the line of force 513 , the primary force 673 decreasing along the line of force 613 . Then, in the regulating driving state, through the interaction of inner and outer control, as in the fifth example, first the target force 582 is reached in point 566 and then the control point 583 .

If for the external control not an oil source but one If the gas source is used, the described rules precede similarly by feeding or releasing gas into the primary upholstery, the amount of oil in the lid-side and bottom oil volume is constant.

After the control point is reached in any way, that or the struts after switching off the outer Regulation left to itself, so that in driving stood only the internal regulation is effective.

On the property of the suspension according to the invention, the driving Erecting up with dynamic driving movements was already pointed out in the introduction.

In the case of a multi-axle vehicle, for example, change to the required wheel loads face each other on a curve the shock absorbers around an equally large vertical load, which is the wheel load Increased on the outside of the curve and reduced on the inside of the curve, outside of the curve deflection results in rebound. The Balancing the drawbar load and the associated erection can only be proportionate when driving due to internal regulation go slowly because there is one for a quick erection Pump rod of large cross section would be required, whose of course periodically changing pump forces the driving comfort would adversely affect.

In the regulating driving state, an uprighting using an oil can source or gas source that does not have any interfering periodic forces generate, take place faster, with appropriate capacity the source so quickly that practically no inclination of the Vehicle takes place and the primary forces through food and from let oil or gas absorb the supporting forces without the internal regulation noticeably the oil distribution in the cover side and oil volume on the bottom changed. This creates compulsive  commonly by eating from a source of high pressure and draining throttle losses into a source of low pressure, the disadvantageous consume energy at times.

These throttling losses can be avoided if the drain line tion of several struts, as mentioned in the introduction, in the entry of an oil pump or a gas compressor and the feed lines from the outlet of the oil pump and the Gas compressor go out so that rebounding from the bottom Shocks spring oil or gas directly into the bottom side Shocks are transported to compensate for the inclination. These The measure can be transferred to other hydropneumatic suspensions.

As already mentioned, the gas compressor together operate with an arbitrarily switchable gas storage equal to the function of the gas source for the static levels take effect.

In the case of oil-side control, the oil pump mentioned can be the static one Level control in such a way that the entry and the outlet of the oil pump one connection line to one Have oil storage, being in the line from the oil storage to When the pump enters a valve device the oil flow from the Drain lines to the oil reservoir and in the line from the outlet to the oil storage a valve device the oil flow from the oil storage lock in the feed lines so that the oil pump is closed Take oil out of the oil reservoir and closed supply lines in the oil reservoir.

In addition to the quick erection described, a Nei construction towards the resultant of gravity and mass force, such as the German patent DE-PS 36 44 931 teaches be caused by the bottom oil volumes the opposite struts directly by a pump device tion are pumped around, whereby the oil volume of one Fe verbeins around the oil volume extracted from the other shock absorber increases and an active inclination control takes place, the Lid-side oil volumes are interconnected and through this connection is an oil exchange between the cover side Oil volume is possible.  

In a four-wheel vehicle that has a torsion-resistant construction has and with four self-pumping struts according to the invention is equipped, a wheel is stopped on a rise ben. Then two diagonally opposite wheels stand up a raised diagonal and two wheels on the other diago nalen. Only the other, the other diagonals can orderly struts have the pump length, while some the struts assigned to the raised diagonals are in the on spring area must be located. If now at regular standstill which rebound a shock absorber up to the mentioned control length, thereby extend the other struts beyond the pump length and in these struts by the internal regulation the load until the pressure equalization between the bottom and Oil volume on the cover side is reduced, one subsequently arises Driving state dangerous load distribution, in which the egg One strut too high and the other one accordingly take over low load share. This load distribution can be there be excluded by that in the struts by suitable means the food is interrupted as soon as the pressure sensor in the other struts a sudden increase in Secondary pressure indicates that with the oil flow through the back flow openings of these struts is connected.

The dangerous load distribution mentioned is in regulating driving condition not to be feared if the drain and feed line against all four struts in the manner already specified Entry and exit of an oil pump or a gas compressor are connected. Then when draining in the struts with the greatest pressure at the bottom, oil or gas is first discharged and in the struts with the smallest when feeding bottom pressure first oil or gas fed, so that Do not build up excessive pressure in any of the regulating struts can.

If an external pump is arranged that pumps oil from the deckelseiti into the bottom-side oil volume, the pump stem can be omitted, which corresponds to the preamble, and a return flow opening as in FIG. 1 can control the pump length. The external pump can also be provided in addition to the pump rod and have a special function, for example pumping up oil up to the control length 603 according to FIG. 5, so that the control length 603 can also be achieved in the regulating standstill without, as in the fifth example, in the range from Pressure stop up to the control length 603 the connection of the bottom oil volume or the primary cushion to the drain line canceled who must.

If the target pressure of the secondary cushion by the outer rain is produced and then an erection of the vehicle with dynamic movements up to level or below With the help of centrifugal agents also beyond Position sensors are carried out on the floor side in a direct way Controlling the feeding and draining of oil or gas becomes the framework not leave the invention.

Claims (9)

1. Hydropneumatic suspension for a vehicle with one or more struts with a piston rod emerging from a housing, which carries a wheel load of the vehicle,

• a sealed piston connected to the piston rod is guided in an oil-filled working cylinder and separates a bottom-side oil volume from a lid-side oil volume,
• the position of the piston determines the length of the spring strut between its fastening elements,
• the oil volume on the bottom is loaded by the gas pressure of a primary gas cushion and the oil volume on the cover side by the gas pressure of a secondary cushion,
• a pump conveys oil from one to the other oil volume and, at a predetermined length of the shock absorber, allows a valve device to flow oil from the other into the one oil volume, so that a pump length of the shock absorber is defined,
• - Preferably, at the bottom of the working cylinder BEFE Stigt pump rod in a hollow piston rod promotes oil in a self-pumping manner from the cover-side in the bottom-side oil volume and a controlled by a control edge of the piston throttled reflux opening after reaching the pump length of oil from the bottom side into the cover-side Oil volume can flow back,
• a gas source or an oil source are provided, with the aid of which the gas pressure of the primary cushion is regulated,

characterized,
that a pressure sensor ( 70 ) detects the pressure of the secondary cushion ( 47 ) and a control element (control slide 21 ) when a setpoint pressure exceeds a connection of the primary pole ( 7 ) to a discharge line ( 12 ) of the gas source and when the setpoint pressure falls below a connection with a Produces feed line ( 13 ) of the gas source, so that in this way the pressure of the primary cushion ( 7 ) is adapted to the wheel load, while the pump length determines the vehicle level. 2. Hydropneumatic suspension according to the preamble of claim 1, characterized in that a pressure sensor ( 70 ) detects the pressure of the secondary cushion ( 47 ) and a control element when a setpoint pressure is exceeded, a connection of the bottom oil volume to a drain line of an oil source and falling below the Setpoint pressure connects to a feed line of the oil well, so that the pressure of the primary cushion of the wheel load is adjusted in this way, while the pump length determines the vehicle level. 3. Suspension according to claims 1 or 2, characterized in that the level of the target pressure is arbitrarily adjustable. 4. Suspension according to claims 1 and 3, characterized in that the drain lines ( 12 ) of several struts open into the inlet chamber of a gas compressor and the feed lines ( 13 ) extend from the outlet chamber of the compressor, so that the compressor, controlled by the pressure sensor ( 70 ), promotes gas directly from the primary cushion of the spring-loaded struts into the primary cushion of the spring-loaded struts to compensate for the inclination of the vehicle during dynamic color movements. 5. Suspension according to claims 2 and 3, characterized in that the drain lines of several struts open into the suction chamber of an oil pump and the feed lines emanate from the pressure chamber of the pump, so that the pump, controlled by the pressure sensor ( 70 ), directly oil promotes the bottom oil volume of the spring struts into the bottom oil volume of the spring struts to compensate for the inclination of the vehicle during dynamic driving movements. 6. Suspension according to claim 5, characterized in that the The suction chamber and the pressure chamber of the oil pump each have a connecting line to have an oil reservoir, in the line from Oil reservoir to the suction chamber a valve device, for example a check valve the oil flow from the drain lines to the Oil reservoir and a valve device, for example a Pressure relief valve the oil flow from the oil reservoir into the feed lines  lock so that the oil pump with the drain lines closed Take oil out of the oil reservoir and keep it closed Feed lines can release oil into the oil reservoir. 7. Suspension according to one or more of claims 1 to 6, characterized in that a control device in the spring deflection area from the pressure stop ( 601 ) to a control length defined by a position sensor ( 603 ) a connection of the bottom oil volume with the feed line of the oil source or Establishes primary cushion ( 7 ) with the feed line ( 13 ) of the gas source and breaks the connection with the drain line, as long as the pressure sensor ( 70 ) reports in this area that the set pressure has been exceeded. 8. Suspension according to one or more of claims 1 to 7, characterized in that a position sensor determines the length of the shock absorber and together with the pressure sensor ( 70 ) or independently of this a desired length of the shock absorber by feeding or releasing gas into the primary cushion ( 7 ) or oil in the bottom oil volume.