Classifications

• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
  • F04B49/10—Other safety measures
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
  • F04B49/06—Control using electricity
  • F04B49/065—Control using electricity and making use of computers
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B2201/00—Pump parameters
  • F04B2201/08—Cylinder or housing parameters
  • F04B2201/0801—Temperature
• • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
  • F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
  • F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
  • F04B2205/00—Fluid parameters
  • F04B2205/11—Outlet temperature

Definitions

• compressors are used in motor vehicles with which a gaseous or liquid medium can be brought to a pressure which is above the ambient pressure.
• This gaseous or liquid medium is often used as a control pressure medium with which actuators such as piston-cylinder arrangements can be acted upon directly or via a pressure medium reservoir.
• One application in motor vehicles results from the need to supply the air springs of a level control system with compressed air in such a way that they can move the vehicle at a distance from the road surface that is appropriate to the driving situation. Since such a level control system does not constantly provide for a height adjustment of the vehicle, a compressor belonging to such a system is only put into operation as required when the need for it exists. Compressors of this type are generally designed as electric motor-operated piston compressors.
• the duty cycle can be varied, for example, depending on the air temperature and air flow velocity in the compressor environment such that the duty cycle is shortened when the compressor ambient temperature increases and is lengthened when it decreases.
• the compressor ambient temperature can be determined using a model calculation from the current vehicle outside air temperature and / or the vehicle engine intake air temperature.
• the disadvantage of this method is that, like all duty cycle methods, it is consistently imprecise because it has the thermodynamic properties of the compressor itself is not taken into account. The control therefore has no influence, for example, on the temperature band in which the compressor is ultimately operated.
• DE 19621 946 C2 discloses a method for temperature-based control of a compressor for air suspension in a motor vehicle, which is designed as an estimation method and does not require a separate temperature sensor on the compressor.
• the compressor is switched off by a control unit when a temperature estimate calculated by it exceeds an upper threshold value, or is switched on or is allowed to be switched on when a lower threshold value is undershot.
• the respective last temperature estimate is increased by a certain temperature jump when the compressor is switched on, the extent of which depends on the level of the last estimate.
• the estimated value is increased by a predetermined positive gradient during compressor operation and decreased by a predetermined negative gradient when the compressor is at a standstill. It is disadvantageous that the linear relationships on which this method is based do not exist in reality, since with large temperature differences the temperature changes are greater than with small temperature differences. In addition, the temperature jump does not take place instantaneously in reality, so that the control-technical availability of the compressor is also disadvantageously reduced in this area.
• the object of the invention is to present a method with which the current temperature at a component of a compressor which is at risk of damage can be estimated more accurately than previously without using a temperature sensor built into the compressor, so that such a compressor is longer than before when component temperatures rise is possible to operate.
• the invention is therefore based on the knowledge that the operating time and the availability of a compressor can be advantageously extended even without using a temperature sensor arranged in the region of the components which are subject to high thermal stress, if the heating and cooling behavior of the compressor can be estimated better than previously.
• the invention proposes, in a further development of the prior art, to determine the cooling and heating properties of the compressor in the form of mathematical-physical models, to store them in a control device and to control the operation of the compressor on the basis thereof.
• the influencing variables U which characterize the characteristic relative temperatures T in a temperature-increasing manner and are taken into account when carrying out the estimation method, include, for example, in addition to the ambient temperature T »of the compressor also the electrical voltage U Kom p at the compressor and the back pressure P of the compression medium downstream of the compressor. With a closed pressure system, the pressure in front of the compressor can also be used.
• these temperature-increasing influencing variables U are incorporated into a heating function B (U) which describes the heating behavior of a specific compressor.
• Tc temperature-reducing influencing variable A
• Tcu suggests that from the last predetermined or calculated values of the relative temperatures Tci,; TC 2 , M the current value of the cooling function A (Tc) is subtracted if the compressor is not in operation in the time interval under consideration, and the current value of the heating function B (U) is added if the compressor is in operation in the time interval under consideration.
• Tc current value of the cooling function A
• U current value of the heating function B
• the initial value of the relative temperatures Tc should be selected so that the estimated temperature T s (Tc) of the compressor corresponds to the value of the ambient temperature T »at the installation location of the compressor.
• this relative temperature T s (Tc) can be initialized with the value zero at the beginning of the compressor control process after a long idle time of the compressor become. This procedure ensures that the temperature estimation method according to the invention delivers exactly the ambient temperature T "after a long cooling time.
• the rough structure of the control method according to the invention as it is stored as software in a motor vehicle control device, for example, can be explained with the aid of the attached drawing.
• the compressor cooling value is calculated in a cooling software module 4 by means of the cooling function A (Tc) stored there and the relative temperature Tc of the last time period provided by the holding element 3, by which the compressor has been calculated since the last calculation cycle due to the characteristics of the compressor and its installation environment cooled down.
• This cooling value is then subtracted from the previous relative temperature Tc (minus sign), so that a new value is formed for the relative temperature Tc.
• the compressor when the compressor is in operation, it causes waste heat, which is recorded by the control device as relevant measured values via heating-specific influencing variables 7 and in a so-called heating module (working memory 5 in the control device) with the aid of a heating function B (U) stored there to a heating value are converted, which takes into account all those influencing factors in the sense of a physical model that increase the temperature of the compressor.
• the cyclically recalculated value of the heating function B (U) is added in particular, but not exclusively, to the current relative temperature Tc when the compressor is switched on (switch 6 with a plus sign), so that a new relative temperature Tc results, which includes both cooling and all heating influence factors to be taken into account if necessary.
• the cyclically current estimation temperature Ts can then be determined in an estimation temperature module 1 for the further operational control (switching on or off depending on the compression requirement and the operating temperature) of the compressor.
• the compressor If the estimated temperature exceeds the permissible upper temperature limit, the compressor must be switched off. However, it is switched on when there is a need for compression and the estimated temperature falls below a lower temperature limit, or when it can be expected that the cooling will be sufficient to carry out a requested actuating task (e.g. a vehicle level change) without overheating.
• a requested actuating task e.g. a vehicle level change
• the control step sequence of a specific control method is presented below, which follows the inventive idea and contains some of the advantageous developments of the invention.
• This process is characterized by the following process steps: a) determining the operating state of the compressor (on or off), b) measuring the back pressure P of the pressure medium downstream of the compressor and / or in the case of closed systems of the upstream pressure in front of the compressor, c) measuring the current one Operating voltage U Kom p of the compressor, d) measuring or estimating the ambient temperature T »of the compressor, e) determining the validity of the influencing variables operating voltage U ⁇ om p and back pressure P or the compressor inlet pressure (admission pressure), f) calculating the current value of the heating function B (U) using heating-specific influencing variables U, g) calculating the current value of the cooling function A (Tc) using the characteristic temperatures of the last time cycle, h) calculating the characteristic relative temperatures Tc ⁇ Tc 2 by adding and / or subtracting the current values of the heating
• the validity of the influencing variables operating voltage U Komp and counterpressure P and possibly upstream pressure are determined by multiplying these values by the value “one” when the compressor is in operation, or be multiplied by the value "zero" when the compressor is not in operation.
• these influencing variables only include variables characterizing compressor heating in the calculation of the estimation temperature Ts (Tc) when the compressor is actually activated.
• the compressor can be switched on if the operating time of the compressor which lasts until the upper threshold value T max is reached is sufficient is to promote a quantity of pressure medium that is sufficient to fill a compressed air reservoir to a certain pressure level and / or to fill air springs of a motor vehicle by a certain filling value.
• Tc Thermal State of the compressor with sufficient accuracy A (Tc) cooling function

Landscapes

• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• General Engineering & Computer Science (AREA)
• Computer Hardware Design (AREA)
• Control Of Positive-Displacement Pumps (AREA)
• Control Of Positive-Displacement Air Blowers (AREA)
• Air Conditioning Control Device (AREA)

Applications Claiming Priority (2)

Publications (2)

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Cited By (2)

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• 2003
  • 2003-07-04 DE DE10330121A patent/DE10330121A1/de not_active Withdrawn
• 2004
  • 2004-04-10 DE DE502004003291T patent/DE502004003291D1/de not_active Expired - Lifetime
  • 2004-04-10 AT AT04726849T patent/ATE357597T1/de not_active IP Right Cessation
  • 2004-04-10 US US10/561,422 patent/US8152475B2/en not_active Expired - Fee Related
  • 2004-04-10 WO PCT/EP2004/003840 patent/WO2005003561A1/fr active IP Right Grant
  • 2004-04-10 EP EP04726849A patent/EP1644640B1/fr not_active Expired - Lifetime

Non-Patent Citations (1)

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