DE4201718C1 - Regulating supply pressure for motor vehicle active hydraulic wheel suspension - carried out in conjunction with pressure storage and pump unit for determining actual and desired pressure values in main supply line and in individual users - Google Patents

Abstract

The desired supply pressure (p) is determined dependent on the alteration speed (f1,f2) of at least one of the determined actual or the computed desired values and is adjusted, so that the desired supply pressure (p) is determined dependent on the highest of all the alteration speeds (fm). The desired supply pressure (p) with determined conditions, is adjusted with the lowering of the values determined from the alteration speed (f1,f2), dependent on the vehicle speed (v). The determined conditions exist if the vehicle speed (v) is zero. ADVANTAGE - Supply pressure is matched to respective instantaneous requirement of hydraulic user, e.g. of active wheel suspension system in simplest manner possible.

Description

The invention relates to a scheme according to Preamble of claim 1.

An electronic rule is known from DE 39 32 475 A1 device known for an active suspension system, that with hydraulic consumers in the form of four Wheel support units is equipped with hydraulic cylinders active depending on various input variables be adjusted. Such input variables are at for example, the actual pressure in the hydraulic cylinders, the Longitudinal or lateral acceleration of the vehicle body as well vehicle acceleration or vehicle speed speed. The electronic control device includes one Pump for generating an oil supply pressure for control oil supply and drainage to adjust the Hydraulic cylinder.

The one generated by this pump Oil supply pressure can ge in different ways be regulated. In DE 39 32 475 A1 is a constant pressure control for generating the oil supply pressure turns. Serves to supply the hydraulic consumers a high pressure accumulator, the oil pumped by the pump records and its oil intake is regulated in such a way that a predetermined pressure value constant in the high-pressure accumulator is maintained. Such a constant pressure control has the disadvantage that the constant to be kept pressure value was higher than for most driving conditions is necessary because it is designed for maximum demand.  

An excessive supply pressure leads to energy losses and thereby to heat the oil. In addition ent stand acoustically, especially when the vehicle is at a standstill cal problems because of the oil flow with a high supply pressure, a high sound pressure level is generated.

Furthermore, an electronic application from the older application according to DE 41 30 395 A1 applies Control device for an active hydraulic wheel suspension system known as, which depends mainly on the Ge speed and lateral acceleration but also from the vertical acceleration of the vehicle regulates the hydraulic fluid.

In addition, there is an electronic control device to regulate the delivery volume for hydraulic supply sher consumers in motor vehicles also from the US 50 62 660 known. With this scheme, too the funding volume depends on the one hand on the vertical Acceleration of the vehicle body and depend on the other gig of the respective value of the relative shift between regulated vehicle body and wheel.

Both in the subject of DE 41 30 395 A1 and in that of US 50 62 660 the regulation is very imprecise because especially the vertical acceleration values on the Whole vehicle are related and not on the acceleration vertical displacement between the vehicle structure and the individual wheels. In addition, each because an additional sensor for measuring the loading acceleration values required.

It is therefore an object of the invention to be as simple as possible che way the supply pressure at the respective moment NEN needs of hydraulic consumers opti times to adjust.  

This object is achieved through the features of the patent claim 1 solved.

According to the invention, the one to be generated by the pump Target supply pressure is not constant on a fixed one Pressure value held, but depending on actual or target Pressure fluctuations, for example in the main supply supply line or in the hydraulic consumers, ver changes. In the event of rapid pressure fluctuations, the target Supply pressure increased with slow pressure fluctuations reduced. The pressure fluctuations, for example one hydraulic consumer, result from the respective speed of change by means of a sensor in the Consumer recorded actual pressure values (actual pressure fluctuations gen) or the target pressure to be set in the consumer values (target pressure fluctuations). To generate the invent According to determined target supply pressure is the Target supply pressure corresponding delivery rate of Pump, for example, by means of an adjustable wobble disc or an adjustable valve.

With electronically controlled hydraulic systems with multiple ren consumers, their respective actual pressure values recorded and their respective target pressure values are calculated, such as e.g. B. in active hydraulic suspension systems with two to four regulated wheel support units several actual and / or target pressure fluctuations or changes speed of actual and / or target pressure values as information for determining the target supply pressure to disposal. In this case, the Target supply pressure after the highest of all determined Rates of change determined or the maximum of be from all rates of change agreed supply pressure values set.  

Thereby is a sufficient target supply pressure for all consumers ensured without being necessarily constant the target set for the maximum possible demand To have to generate supply pressure.

Through this regulation according to the invention, a simple, precise and quick determination of the target supply possible to adjust the pressure. Beyond that no additional sensor devices required because in known electronic suspension systems without towards sensors for recording actual pressure values and others input signals and a computer to determine the Target pressure values from these sensor signals are available.

An advantageous development of the invention is the Ge Subject matter of claim 2.

The vehicle speed is in control devices Motor vehicles compared to pressure sensor signals even more commonly used input signal. So stand there electronically controlled hydraulic system in addition to the actual pressure values in the hydraulic consumers also the vehicle speed is available, he will according to the target supply pressure at certain Conditions, e.g. B. in driving conditions with increased requirements computing capacity or with lower requirements accuracy, while avoiding the expense more determination from the rates of change of the recorded actual or calculated target pressure values in Ab dependence on the vehicle speed determines how for itself known.

With increasing vehicle speed the The pressure fluctuations in hydraulics are also mandatory rule consumers such. B. in the wheel support units. Thus, even with increasing vehicle speed  the target supply pressure increases. The target supply printing can also be done using an experiment and map stored in the computer Vehicle speed ranges are assigned.

In addition, e.g. B. in the event of failure of the components for the pressure fluctuation-dependent control method of the target Supply pressure are required on the vehicle speed-dependent control method can be avoided.

This development of the invention therefore offers a redun dante system that is flexible to different vehicles React conditions, recognize errors and when they occur an error can remain functional.

Another advantageous development of the invention is Subject matter of claim 3.

The only vehicle speed-dependent Re Gel method is dependent on vehicle speed conditions with less exacting requirements regulation, especially at very low vehicle speeds used or when the vehicle is at a standstill. Here is not a precise regulation with an evaluation of the pressure fluctuations are necessary, a target ver is sufficient supply pressure, the vehicle speed values of Zero is assigned and that as a defined minimum pressure on the one hand low noise generation and on the other hand if necessary Reaching the maximum pressure to be generated within a defined ensures the smallest time interval. A third embodiment of the invention is the counter State of patent claim 4.

In the event of error-free operation, the target Supply pressure from both the vehicle speed as well as from the rates of change of the actual or Target pressure values are determined, after which several target suppliers supply pressure values are available. Is it out of driving  tool speed z. B. based on an average driving path ripple determined target supply pressure value z. B. at Driving on a smooth road greater than all of the rates of change of the Actual or target pressure values Supply pressure values, becomes the maximum value, that is, the setpoint determined from the vehicle speed Supply pressure value actually set, and so one certain reserve against the sudden occurrence of impacts etc. created.

In the drawing is an embodiment of the Erfin shown. It shows schematically in four figures an inventive determination of the target supply pressure for an electronically not shown here regulated hydraulic wheel support system both dependent on the vehicle speed, as well as depending on the maximum rate of change of the respective actual Pressure values in the cylinders of two wheel support units. It demonstrate

Fig. 1 shows the time profiles of the pressure fluctuation values f ₁ and f ₂ in two Radtrageinheiten in the form of frequencies and the selection of the respective maximum value f _m of the two at the sampling times t ₁ to t ₇ measured pressure variation values f ₁ and f _2,

FIG. 2 shows the assignment of an offset printing _{offset p; m} from the offset pressure values p ₀ to p _{7 f} to the selected through the Maxi malwerte f _{m f} frequency ranges B1 to B8,

Fig. 3 is _offset assigning an offset pressure p _v of the offset pressure values p ₀ to p ₇ schwindigkeitsbereichen to the Fahrzeugge B1 _v to B4 _v, the present by at the sampling times t ₁ to t ₇ vehicle speed values v are selected, and

Fig. 4, the composition of the target supply pressure of a constant minimum pressure component _c p and ei nem variable pressure component in the form of offset values p ₀ to p _7.

In FIG. 1 are provided at each sampling time t ₁ to t _7, two pressure fluctuation values f ₁ and f _2, z. B. in the form of Fre frequencies, the highest of these two values being designated f _m . A range from the frequency ranges B1 _f to B8 _{f is} assigned to each of these values f _m . The areas shown here on the ordinate can be found in Fig. 2 on the abscissa again. Depending on the frequency range _f B1 to B8 _f in Fig 2 an off setdruck _{offset p;. M} from the available range offset pressure values p ₀ to p ₇ assigned. The offset pressure p _{offset; m} resulting from the maximum pressure fluctuation values f _m is a possible variable pressure component, which is added to form a constant supply pressure component (p _c see FIG. 4) to form the target supply pressure.

The same offset pressure values p ₀ to p ₇ from FIG. 2 are also available in FIG. 3 for determining a vehicle speed-dependent offset pressure p _{offset; v} . The offset pressure p _{offset; v} is assigned to the vehicle speed ranges B1 _v to B4 _v , which are predetermined as a function of the vehicle speed values _{v available} at the sampling times t ₁ to t ₇ . The vehicle speed v, divided into these areas B1 _v to B4 _v , is plotted on the abscissa.

At each sampling instant t ₁ to t ₇ results from Figures 1 and 2 a maximum pressure variation dependent offset pressure value P _{offset;. M} and from Figure 3, a fahrzeuggeschwin digkeitsabhängiger offset value _{offset p;. V.} Both offset pressure values are a selection from the offset pressure values p ₀ to p ₇ . At each sampling time, the higher of these two offset pressure values (p _{offset; m} , p _{offset; v} from p ₀ to p ₇ ) is selected and added as the maximum offset pressure value p _{offset; max} in FIG. 4 to the constant minimum pressure component p _c . The maximum offset _pressure value p _offset that results at each sampling time t ₁ to t _{7 ; max} is also the respective value p ₀ to p ₇ , which in FIG. 2 and / or FIG Circle marked sampling time point t ₁ to t ₇ results. The target supply pressure values p resulting from the constant minimum pressure component p _c and the respective maximum offset pressure values p _{offset; max} are entered in FIG. 4 via the sampling times t ₁ to t ₇ likewise marked with a circle with a dotted circular area. Thus, the pressure curve p drawn in FIG. 4 represents the time curve of the target supply pressure to be generated by the pump.

. To illustrate the hitherto general description of this embodiment, Figures 1 to 4 are based on the sampling instants t _2, t ₄ and t ₆ in the following be explained in more detail:

For example, the (frequency) range B2 _f results from FIG. 1 at the sampling time t ₂ with the maximum value f _m from the pressure fluctuation values f ₁ and f ₂ . Referring to FIG. 2, this area _f B2 assigned an offset pressure value _P1. At the same sampling time t ₂ , the vehicle speed v results in the selection of the (vehicle speed) range B1 _v to which an offset pressure value p _{0 is} assigned. A maximum selection of these is the sampling time t ₂ from the offset pressure curves p _{offset; m} and p are _{offset; v} resulting offset values p ₁ and p ₀ gives the maximum offset value _offset p _max of p. ₁ In Fig. 4, this value p _{1 is added} at the sampling time t ₂ as a variable pressure component to the constant minimum pressure component p _c .

At the time of sampling t ₄ , the range B5 _f results from FIG. 1 from the maximum pressure fluctuation value f _m . B5 from _f 2, an offset value results shown in Fig _{offset p;. M} of p _4. Moreover, the offset value of Figure 3 at the sampling time t ₄ from the offset pressure curve p _{offset;. V} is equal to _p0. This results in a maximum offset _pressure value p _{offset; max} of p ₄ . This value is in turn added to the constant minimum pressure component p _c at the sampling time t ₄ in FIG. 4.

In both examples, at sampling time t ₂ and at sampling time t ₄ , the maximum offset pressure value p _{offset; max is determined} as a variable pressure component for determining the target supply pressure by means of the maximum pressure fluctuation value f _m or the offset pressure curve p _{offset; m} . Therefore, the reference symbols "t ₂ " and "t ₄ " are also marked with a circle in FIG. 2. At the sampling time t ₆ , however, the maximum offset _pressure value p _{offset; max} results from the vehicle speed v or the offset _{pressure curve} p _{offset; v} at p ₇ .

At the time of sampling t ₄ , the vehicle speed value v equal to zero means that the vehicle is at a standstill. However, the opposite information is provided by the high pressure fluctuation values f ₁ and f ₂ , which are also in the areas B4 _f and B5 _f , likewise at the sampling time t ₄ . Such a plausibility check suggests that the vehicle speed signal v has failed at the sampling time t ₄ . If such an error were also to be recognized in the subsequent sampling times, an error message can be stored, for example, and the variable pressure component is subsequently formed exclusively from the offset printing curve p _{offset; m} .

It should finally be pointed out that the step-shaped pressure curves shown in Fig. 2 to Fig. 4 merely serve as an example. The pressure profiles can be of any shape. For example, continuous or ramp-shaped courses as well as representations in tabular form according to experimentally determined maps are possible.

Claims (4)

1. Regulation of the supply pressure for hydraulic consumers in motor vehicles in connection with a pressure accumulator and a pump, in particular for consumers of active hydraulic suspension systems, with a device for detecting the actual pressure value in the main supply line and / or in the individual consumers and to determine the target pressure values for the main supply line and / or for the individual consumers, characterized in that the target supply pressure (p) depending on the rate of change (f ₁ ; f ₂ ) at least one of the detected actual or calculated target -Pressure values are determined and set, the target supply pressure (p) being determined as a function of the highest of all rates of change (f _m ). 2. Regulation according to claim 1, characterized in that the target supply pressure (p) is set depending on the vehicle speed (v) under certain conditions while ignoring the values determined from the rate of change (f ₁ ; f ₂ ). 3. Regulation according to claim 2, characterized ge indicates that one of the certain conditions exists, when the vehicle speed (v) is zero. 4. Regulation according to claim 2 or 3, characterized in that one of the certain conditions is present when the depending on the vehicle speed (v) certain target supply pressure (p) is greater than that depending on the rate of change (f ₁ ; f ₂ ) certain target supply pressure (p).