Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D5/00—Power-assisted or power-driven steering
  • B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
  • B62D5/062—Details, component parts
  • B62D5/064—Pump driven independently from vehicle engine, e.g. electric driven pump
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
  • B62D—MOTOR VEHICLES; TRAILERS
  • B62D5/00—Power-assisted or power-driven steering
  • B62D5/06—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle
  • B62D5/065—Power-assisted or power-driven steering fluid, i.e. using a pressurised fluid for most or all the force required for steering a vehicle characterised by specially adapted means for varying pressurised fluid supply based on need, e.g. on-demand, variable assist

Definitions

• the invention relates to a method for controlling a hydraulic power steering pump unit for a motor vehicle.
• More and more motor vehicles are equipped with hydraulic steering assistance systems, comprising a hydraulic cylinder able to move a steering rack, according to a desired rotation of the wheels, detected at the steering wheel of the steering column. direction.
• the hydraulic cylinder is actuated by an electric pump unit or GEP comprising an electric motor, a pump, a reservoir of hydraulic fluid or oil, and an electronic control unit or
• the electronic control unit controls the electric motor which rotates the assist pump.
• the booster pump supplies pressurized fluid to the cylinder through a servovalve which directs the oil to one or other of the cylinder chambers depending on the direction of rotation desired for the vehicle wheels.
• the rotational speed of the assist electric motor determines the available cylinder pressure, which is the mechanical assist power that the driver of the vehicle can expect from the system.
• the assistance power required is especially important for maneuvers when stationary or when the vehicle is traveling at low speeds, or for some maneuvers when the vehicle is traveling at higher speeds and when the driver is printing a high angular speed at the steering wheel.
• the electronic control unit adjusts the speed of the assistance engine according to the speed of the vehicle and the speed of variation of the angle of the steering wheel.
• this method assumes that the electronic control unit is connected to the tachometer or to a central data bus to collect the speed of the vehicle, and that it is also connected to a steering wheel angle sensor.
• Such a steering wheel angle sensor often represents a specific investment for the assistance engine control, because the servovalve adapts to the variations of angles of the steering column, but does not provide a signal usable by others. systems.
• the patent application FR 2 864 000 proposes to recalculate the steering wheel angle variations as a function of variations in the current consumed by the assistance engine. This method does not give full satisfaction because the system remains dependent on the speed of advance of the vehicle, and the proposed method of calculating the steering wheel angle is very approximate.
• the aim of the invention is to limit the consumption and noise of the assistance engine better, while guaranteeing a satisfactory level of comfort and safety of the assistance device, thanks to a simple, reliable and cost - effective device. low cost.
• the invention relates to an electrohydraulic power steering system for a motor vehicle comprising a hydraulic pump driven in rotation by an electric motor and supplying at least one jack connected to a steering column.
• the rotational speed of the engine is regulated by an electronic control unit according to the current consumed by the engine.
• the electronic control unit is configured to perform the following actions:
• the vehicle being at a standstill, it starts the electric motor of the electric pump unit and it slaves it at a first speed of rotation of idle, the vehicle being at a standstill or no longer being stationed, it then compares the current consumed by the engine with a first high threshold value,
• the electronic control unit is configured to perform the following actions:
• the motor if the current consumed by the motor is lower than the first threshold low value, it reduces the rotational speed regulation of the electric motor at the first idling speed.
• the electronic control unit is configured to maintain this engine speed at a set speed. constant equal to this second assistance rotation speed, or at set speeds at least equal to the second assistance rotation speed, as long as the driver of the vehicle does not decide to stop the vehicle completely.
• the first high threshold value is between 5A and 20A, preferably between 10A and 15A
• the first threshold low value is between 2A and 15A, preferably between 5A and 10A, the first threshold high value being greater than the first threshold low value.
• Some embodiments may provide more than one assist rotation speed, so more than two set speeds.
• the electronic control unit when the rotational speed of the electric motor is slaved to the second assist rotational speed, or respectively to an umpteenth rotational speed of assistance greater than the second, the electronic control unit is configured to perform the following actions: it compares the current consumed by the motor, to a second, or respectively, to an uth higher threshold value,
• the nth upper threshold value if the current consumed by the motor is greater than the second or, respectively, the nth upper threshold value, it increases the rotational speed reference regime of the electric motor to a third, or respectively, to a (n + 1) th assistance rotation speed.
• the electronic control unit is configured to maintain the engine rotation reference speed constant as long as it does not detect a high threshold value or a low threshold value.
• the number of high threshold values programmed in the electronic control unit can be between 1 and 4, preferably between 1 and 2.
• the first idling speed is between 800rpm and 2000rpm
• the second assist speed is between 2000rpm and 6000rpm
• a third motor assist rotation speed can be provided, for example between 3000 rpm and 6000 rpm.
• the electronic control unit is configured to, after detecting a high current threshold value, progressively increase the revolutions of the electric motor in a time interval between 0.05s and I s, and, if it detects a low value of current threshold, to progressively change the regime of the electric motor down in a time interval between 0.5s and 5s.
• the subject of the invention is a method for controlling an electric pump unit intended to supply a steering assistance system for a motor vehicle.
• the electric pump unit comprises an electric motor driving a hydraulic pump, supplying at least one jack, the method comprises the following steps:
• the power consumed by the motor is then compared with a first high threshold value
• the rotation speed of the electric motor is increased to a second assist rotation speed.
• FIG. 1 is a diagrammatic representation of an electrohydraulic steering assistance system for a motor vehicle
• FIGS. 2a and 2b are examples of current and speed curves of a driven EPG engine according to the invention
• FIG. 3 is an example of a control algorithm of a PEG engine according to the invention
• FIG. 4 is another example of a control algorithm of a PEG engine according to the invention.
• an electro-hydraulic power steering system 1 comprises a steering wheel 2 and a steering control shaft 3 (schematized by its longitudinal axis), enabling the user to determine the orientation of the steering systems. steering wheels of his vehicle.
• the steering shaft 3 is engaged with a rack 7 by means of a rotary pinion 4.
• the rack 7 is slidably mounted in a tubular housing 8, and is integral with a piston 15 which separates two sealed chambers of the tubular housing 8.
• the space comprising the two chambers and the piston constitutes a hydraulic cylinder 9.
• the left and right ends of the rack 7, covered and protected by bellows 22, are connected by means of joints 1 1 to rods 12 which modify the orientation of the left and right steering wheels of the vehicle when the rack 7 moves relative to the housing 8.
• the movement of the rack 7 can be obtained either directly by the kinematic chain connecting the steering wheel the rack by means of the rotary pinion 4, or by the joint action of the cylinder 9.
• the cylinder 9 can receive fluid under pressure in a first chamber through a pipe 20a, or in a second chamber through a pipe 20b.
• An assistance valve 6 makes it possible to detect the orientation of the steering control shaft 3 and to send fluid under pressure into the pipe 20a or into the pipe 20b depending on the orientation of the control shaft. direction 3, so that the force of the cylinder is added to the force exerted through the rotary pinion.
• the orientation of the control shaft can be hydraulic (by placing in progressive communication of certain channels of the hydraulic circuit) or electronic (by an angle sensor).
• the assistance valve 6 receives fluid at high pressure through a supply line 25 connecting it to a pump 14, and returns reduced pressure fluid through a return line 26 to a hydraulic fluid reservoir 17.
• An electro group propellant (GEP) 13 comprises the hydraulic pump 14, rotated by an electric assist motor 16, the hydraulic fluid reservoir 17, and an electronic control unit (ECU) 18 which drives the motor 16 via a connection 23 the ECU 18 comprises, in a conventional manner, a microprocessor or central unit, random access memories, read-only memories, analog / digital converters and various input and output interfaces.
• the pump 14 brings to a suitable hydraulic pressure, fluid that it takes in the reservoir 17 and that it sends into the supply pipe 25.
• the ECU 18 receives by a connection 24 a signal indicating the current consumed by the motor 16.
• the ECU 18 is connected to a table of values 27. values 27 can also be directly stored in an internal memory of the ECU.
• the ECU 18 receives an electrical signal related to the vehicle speed information parameter by a speed sensor (not shown) provided on the vehicle.
• a speed sensor not shown
• an angle sensor 19 mounted at the assistance valve 6, returns to the ECU 18, through a line 21, the information related to the steering wheel 2, that is to say a signal electric related to the steering wheel speed parameters and steering wheel angle.
• the ECU 18 calculates a target value of the rotational speed of the motor 16 based on the vehicle speed signal, the steering wheel speed, and the steering wheel angle.
• the ECU 18 does not receive a signal from a steering wheel angle sensor. This eliminates the presence of a specific angle sensor and connection 21.
• Specific angle sensor means a sensor capable of transmitting a signal usable by the ECU, representative of the angular position of the steering control shaft 3).
• the ECU 18 may have or not have a vehicle speed signal. In embodiments where the speed of the vehicle is not returned to the ECU 18, a passage of connection wires is saved, as well as a re-amplification stage of the speed signal thus distributed.
• FIGS. 2a and 2b show two characteristic curves of the operation of a GEP included in a device of FIG. according to the invention, for example a GEP 13 corresponding to the configuration of FIG. 1, without a steering angle sensor 19 or a connection 21.
• curve 30 of FIG. 2a represents the current I consumed by the assistance motor 16 over time.
• Curve 31 of Figure 2b represents the rotation speed setpoint N GEP imposed on the assist motor 16 by the ECU 18 on the same time interval.
• the N GEP engine speed of the GEP is slaved to a value r n which can be for example an idle speed between 800 revolutions / minute and 1500 rpm.
• GEP remains constant and equal to a first value I 1 .
• the driver of the vehicle starts to maneuver the steering wheel, which has the effect of increasing the pressure in the hydraulic assistance circuit of the vehicle, resulting in an increase in the current I consumed by the engine of the GEP.
• the value I of the current consumed by the GEP motor passes above a high value of threshold Sh.
• the ECU 18 of FIG. 1 detects this crossing of the threshold Sh, and varies the speed regulation of the engine of the GEP to bring it in a time ⁇ m from its initial value r n to a new value r n + i superior to the previous one.
• the value r n + i may for example be a rotation speed around 2500 rpm, which allows the pump 14 to deliver sufficient hydraulic assist pressure for maneuvers of reduced amplitude.
• the current I consumed by the engine of the GEP then stabilizes around a value I 2 greater than the high threshold value. Sh.
• the current I begins to decrease substantially due to a decrease in the reaction of the wheels on the steering shaft. This lesser force of interaction between the wheels and the steering shaft may be due either to the fact that the driver reduces or stops his action on the steering wheel, or to the fact that the speed of the vehicle has increased, so that the effort required to turn the wheels decreases.
• the curve 30 passes at point 33 below a low threshold value Sb less than high value of threshold Sh.
• the ECU 18 detects this threshold crossing and, over a time interval ⁇ d, reduces the speed reference of the motor of the GEP to gradually bring it from the value r n + 1 to the value r n .
• the engine of the GEP is then found again in "sleep" mode with a reduced power consumption, close to the initial standby current I 1 , or even equal to this current I 1 .
• the sequence of previous events is an illustration of how the GEP engine can be controlled to switch from a sleep mode to an active mode and then return to a sleep mode.
• the same principle can be applied by changing the values of the regimes r n , r n + 1 , and the high and low values of the current thresholds Sh and Sb, to control the transition of the GEP from a mode of assistance characterized by the rotating r n to a higher level of assistance mode corresponding to a rotational speed of the engine r n + i greater than r n .
• the electronic control unit can thus successively impose on the GEP engine a standby mode, then one or more assistance modes, the transition to the higher regime being each time conditioned by the crossing of a high value of the current threshold. Sh, and the possible return to the lower regime being conditioned by the crossing of a low value of current threshold Sb lower than Sh.
• the difference in level between the threshold Sb and the threshold Sh which can be advantageously of the order of five amperes, not to reduce too quickly the last level of assistance selected, in case the driver would perform a new maneuver requiring a similar power assistance.
• a curve 30 of current I which is a filtered curve of the current actually drawn by the motor of the PG.
• the filter used for the current I can be chosen so as to reduce the amplitude of the accidental current peaks.
• the filter may also be selected to introduce a time delay of the consumed current. This establishes a window of observation during which the upward or downward trend in the variation of the current I consumed can be confirmed or not confirmed.
• the electronic control unit When the GEP leaves the "sleep” mode or when it switches to a higher assistance mode, the electronic control unit imposes the transition from the previous regime r n to the upper regime r n + i in a time interval ⁇ m enough short, typically of the order of a tenth of a second.
• the electronic control unit makes the transition of the system. higher than the lower regime more gradually, for example in a time ⁇ d between 1 and 5 seconds.
• the "sleep" mode can be activated only when the vehicle is started, and the EPG either remains in the same assistance mode, or stays at least at a minimum assistance level higher than the standby mode, until the driver stops the vehicle for an extended period of time, for example at the end of the journey, by cutting off the contact at the dashboard.
• some variants of this driving strategy may require maintaining the assistance scheme. minimum; other variants may opt for an engine shutdown of the GEP and a new passage by the idle speed as the initial start of the vehicle.
• GEP can return to "sleep" mode as the current I consumed by the motor 16 returns below a first low threshold value Sb.
• the engine of the GEP returns to idle idle, before stopping when the driver turns off the ignition on the dashboard of the vehicle.
• the engine of the GEP goes down to the standby mode.
• it can then be switched off at the same time as the engine, or remain in standby mode.
• Alternative management strategies may be envisaged where the electronic control unit imposes one, imposes two, or imposes three different assistance regimes for the rotation regime of the control unit.
• motor 16 of the GEP for example a first level of assistance between 2000 rpm and 3000 rpm, for example 2500 rpm, a second level of assistance between 3000 rpm and 4000 rpm, for example of 3800 revolutions / minute, and possibly a third level of assistance superior to
• FIG. 3 represents an example of an algorithm 30 according to which the electronic control unit 18 of FIG. 1 can drive a motor 16 of GEP.
• the electronic control unit has a series of values stored in a table 27 shown on the left of Figure 3.
• This table contains a first value ri corresponding to a rotation of engine idle rotation of the GEP. It also contains a value r 2 corresponding to a first-level rotation regime of PEG engine assistance. It may also contain a value r 3 corresponding to a second level scheme of assistance from the PEG engine, and possibly one or more other values r n + i corresponding to regimes of the nth level of assistance of the PEG.
• Table 27 also contains current threshold values, in particular a first high value of threshold Sn 1 corresponding to the value of current I consumed by the motor 16 of the GEP, above which the electronic control unit 18 imposes on the motor 16 of the GEP to leave the "sleep" mode, and a first threshold low value S ib corresponding to the current threshold below which the electronic control unit resets the engine of the GEP in "sleep” mode, it is i.e. to the rotation regime ri.
• the table 27 may also contain an uth upper threshold value S n h above which the electronic control unit switches the engine speed r n r n regime to r n + i corresponding to the umpteenth assistance mode. It then also contains an umpteenth low threshold value S nb below which the electronic control unit resets the GEP of the umpteenth assistance mode to a (n-l) th mode of assistance, that is, that is, a driving speed of the GEP equal to r n .
• the values of the table 27 are the same as those used in the algorithm shown on the right of FIG. 3. In the initial step 31, following a command to start up the corresponding engine of the vehicle, power-up at the dashboard of a group of vehicle components, the
• the electronic control unit 18 initializes a status indicator n to the value 1, and imposes a first rotational speed ri the engine of the GEP.
• the electronic control unit then performs a test 32, to check if the current I consumed by the engine of the GEP has become higher than a first high threshold value S n 1 . If the current I has not yet crossed this threshold, the electronic control unit performs a test 33 to check if the contact of the dashboard has been cut. If not, the electronic control unit again tests whether the current I has become greater than the threshold Sn 1 by returning to the test step 32.
• the electronic control unit detects that the current I has become greater than the threshold S n 1 , it increments in step 34 the state indicator n to the value 2 and imposes the rotation regime r 2 which is the first level engine assistance scheme of the GEP.
• the electronic control unit In the case where the electronic control unit is configured to vary the GEP regime between several levels of assistance, the electronic control unit then tests at step 35 whether the current I consumed by the GEP engine has crossed an uth highest value of mourning S n h, that is to say, at this step, a second high value of threshold, since na is currently the value 2. If the current I has crossed this threshold S n h, l the electronic control unit tests in step 36 whether the step indicator n is still strictly less than the value m - 1 corresponding to the step indicator of the penultimate level of assistance. If not, that is, if one is already at the penultimate level of the highest assistance of the GEP, the electronic control unit increments in step 37 the indicator.
• step n the electronic control unit tests in step 38 whether the current I consumed by the GEP motor has returned to below the threshold S ( m _i) b. If the answer is no, the control unit performed again the test electronics 38. If the answer is positive, the electronic control unit decrements in step 39 the flag of step n to bring it to the value m-1, and imposes the speed of rotation r m _i the engine of the GEP corresponding to the penultimate scheme of assistance the highest.
• step 36 the electronic control unit finds that the state indicator n is actually strictly less than the value m - 1, it increments in step 40, the status indicator of a unit and increases the speed of reference of rotation of the motor of GEP for the bring the value r n to the value r n + 1 .
• the electronic control unit then returns to the test step 35.
• the electronic control unit finds that the current I consumed by the EPG engine is not passed above the nth upper threshold value S n h, then the electronic control unit tests in step 41 whether the current I has passed below a (n-l) th low threshold value S ( n-1 ) b- If this is not the case, the electronic control unit returns to the test step 35. If the current I has passed below the test step 35.
• step 42 the electronic control unit tests whether one is at a higher assistance level than the first. If this is the case, the electronic control unit decrements the state indicator n by one unit in step 43, and reduces the rotation speed of the engine of the GEP to change to the rotation speed r n _i corresponding to the lower level of assistance.
• the electronic control unit then returns to the test step 35. If in the test step 42, the electronic control unit finds that it is at the first level of assistance, then the electronic control returns to the "sleep" configuration corresponding to step 31. It then resets the status indicator to the value 1 and imposes the rotation speed ri corresponding to the engine standby mode of the GEP. It then continues the previous test steps from test 32.
• the electronic control unit shuts down the engine of the GEP when, after going into "sleep" mode in step 31, it finds by performing the test 33 that the vehicle was deliberately stopped by cutting the contact of the dashboard.
• FIG. 4 illustrates another algorithm 30a for controlling a GEP motor as a function of the current consumed.
• the engine of the GEP only runs in idle mode ri during the time interval separating the starting of the vehicle and the first time when the current consumed by the engine of the GEP crosses a first high value of threshold Sn 1 .
• the GEP first goes through the idle mode in step 31, after the start of the engine of the vehicle, then, successively, when the current I consumed by the GEP engine passes a first high threshold value Sn 1 , the GEP goes to step 34 in "first level of assistance" mode with a pump speed equal to r 2 , then, when the current I becomes greater than a second high threshold value S 2 h, the GEP goes to step 34a to a second level of assistance where the pump motor is brought to a set speed r ⁇ .
• the variation of current consumed or the derivatives of the consumed current can be used instead of the value of current consumed by the assistance engine.
• the value of the vehicle speed which does not give rise to an additional sensor but requires a specific connection with the EPU of the EPG, can be used to more precisely determine the rotation speed of the assistance engine in the frame. each level of assistance.
• the embodiment of the invention in the form of logic blocks or in the form of calculation blocks can be made from electronic components or physically independent calculators, or by programming all the logic blocks and the calculation blocks described in the form. software.
• the corresponding program, as well as its sub programs, can be implemented in one or more computers, integrated or not to a central electronic control unit.
• the control device makes it possible to limit the electrical consumption of the group GEP, thus the ecological footprint of the vehicle, and makes it possible to reduce the level of noise in the passenger compartment, which improves the comfort of the occupants of the vehicle.
• This control system requires only local information: the value of the motor current. This eliminates the causes of failures such as deterioration of connection lines (connections to data sources - steering wheel, speed of the vehicle - remote GEP), or accidental disconnection, including vibration, these connection lines.
• a judicious choice of the high and low threshold values of each level makes it possible to keep a sufficient availability of the assistance hydraulic power, and to avoid untimely passages from one level of assistance to another.
• the calculation of the engine speed is particularly simple, which also contributes to the robustness of the system, and therefore to the safety of the occupants.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Combustion & Propulsion (AREA)
• Transportation (AREA)
• Mechanical Engineering (AREA)
• Steering Control In Accordance With Driving Conditions (AREA)
• Power Steering Mechanism (AREA)

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• 2009
  • 2009-04-08 FR FR0952302A patent/FR2944250B1/fr not_active Expired - Fee Related
• 2010
  • 2010-04-07 EP EP10723223A patent/EP2417003A1/de not_active Withdrawn
  • 2010-04-07 CN CN201080025214.4A patent/CN102458961B/zh not_active Expired - Fee Related
  • 2010-04-07 RU RU2011145035/11A patent/RU2011145035A/ru not_active Application Discontinuation
  • 2010-04-07 WO PCT/FR2010/050673 patent/WO2010116091A1/fr active Application Filing

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