EP1598555A1 - Motor pump unit having means to limit the pressure of the hydraulic fluid which is being pumped by said pump - Google Patents

Abstract

The system has a hydraulic pump (3) driven by an electric motor (2) to provide hydraulic power to a hydraulic device (4). A controller (13`) has a microprocessor (17) for calculating a limited maximal current to be supplied to the motor for controlling the rotational speed of the motor and limiting the pressure of a hydraulic fluid supplied by the pump in a hydraulic circuit.

Description

The invention relates to an electro-pump group system, of the type comprising an electric motor, a pump driven by the electric motor and intended to provide hydraulic power, and means of limitation of the hydraulic fluid pressure in the hydraulic circuit.

In electropump systems of this type, which are known, the function of the pressure limitation is accomplished by a mechanical pressure limiter in the form of a safety valve provided with a spring-loaded relief valve. prestressing adjustable according to the maximum permissible pressure for a given application. As can be seen in FIG. 1, which shows a known electropump system for a motor vehicle where the pump is intended to provide assistance to the steering of the vehicle and indicates in 1 generally the electric pump unit, in 2 the electric motor, in 3 the hydraulic pump, in 4 the cylinder device supplied with hydraulic fluid by the pump 3, in 5 the wheels of the vehicle, in 6 the flywheel, in 7 the steering column, the pressure limiter noted 8 is placed between the pump and the cylinder 4. In case of overpressure, the valve indicated diagrammatically at 9 of the limiter 8 opens a bypass lane 10 which is connected to the tank 11 of the liquid to be sucked by the pump 3. It is still it should be noted that FIG. 1 illustrates at 12 the electric power supply battery of the electropump 1. The figure also shows that the electro-pump unit 1 receives the information on the speed of rotation of the steering wheel, denoted V _VO. , and the inf ormation on vehicle speed V _VEH .

The use of the mechanical pressure limiter 8 in the known system has many disadvantages major. Indeed, it causes an additional cost, is cumbersome, can cause states of instability, generates noises acoustics related to its opening and, by constituting a specific mechanical part, decreases the reliability of the system.

The present invention aims to propose a electro-pump group system, which overcomes disadvantages inherent in the known system.

To achieve this goal, the system according to the invention is characterized in that the means for limiting the pressure are realized in the form of management electronic.

• la figure 1 est une vue synoptique en forme d'un schéma bloc d'un système de groupe électro-pompe selon l'état de la technique ;
• la figure 2 est une vue synoptique, similaire à la figure 1, d'un système d'électro-pompe selon l'invention ;
• la figure 3 montre le schéma synoptique du calculateur contrôleur 13' du groupe électro-pompe selon la figure 2 ;
• la figure 4 est un schéma synoptique illustrant la mise en oeuvre des opérations effectuées par le calculateur 13' de la figure 3 ;
• les figures 5 et 6 sont des schémas synoptiques similaires à la figure 4 et illustrent deux autres versions de mise en oeuvre du calculateur/contrôleur 13' d'un groupe électro-pompe selon l'invention.

The invention will be better understood, and other objects, characteristics, details and advantages thereof will appear more clearly in the explanatory description which follows, with reference to the appended schematic drawings given solely by way of example, illustrating two modes of embodiment of the invention and in which:

• FIG. 1 is a schematic block diagram of an electropump system according to the state of the art;
• FIG. 2 is a synoptic view, similar to FIG. 1, of an electropump system according to the invention;
• FIG. 3 shows the block diagram of the control computer 13 'of the electric pump unit according to FIG. 2;
• FIG. 4 is a block diagram illustrating the implementation of the operations performed by the computer 13 'of FIG. 3;
• FIGS. 5 and 6 are schematic diagrams similar to FIG. 4 and illustrate two other versions of implementation of the computer / controller 13 'of an electric pump unit according to the invention.

Referring to Figure 2, which gives the diagram synoptic of a system of assistance to the management of a motor vehicle, using an electric pump according to the invention, it is found that the latter is distinguished of the electro-pump group known from the state of the art, shown in FIG. 1, in that the limiter of pressure is removed and that the function performed in the known system by the limiter is accomplished by means electronic pressure reliefs that are part of the 13 'calculator / controller and are indicated by the zone hatched 15 of the bin representing this calculator. On the FIG. 2 uses the same reference as in FIG. for identical elements.

It should be noted that in a set of groups electropump, the pump transforms the speed of rotation of the electric motor 3 in hydraulic flow in the circuit hydraulic, namely the cylinder 4. The resistant torque exerted on the engine is the sum of the torque resistant to pressure in the hydraulic circuit and the resistant torque of the pump, the resistant torque related to the engine that can be considered negligible. By therefore, limit the pressure in the hydraulic circuit is equivalent to limiting the torque provided by the engine. Thus it has proved possible in the context of the invention, to obtain the limitation of the pressure in the circuit hydraulic by limiting the maximum current to be sent to the electric motor 2 driving the pump 3.

According to one characteristic of the invention, the maximum limiting current I _LIM is determined according to three parameters, namely the supply voltage U _BAT supplied by the battery, the temperature T _MOS of the active electronic elements, namely transistors. used and the temperature T _CA of the carrier board electronic components calculator. The values of the limit current I _LIM vary according to these parameters and are taken in a calibration table made from tests. Thus each group of three battery voltage and temperature values corresponds to a limit current value I _LIM . This interdependence is shown in Figure 4 at 19a in the form of a three-dimensional diagram of the three axes which are respectively carried U _BAT temperatures, temperatures of _MOS active elements T and temperature map T _AC, next of the table of values. From the established values, the intermediate values of I _LIM are obtained by linear interpolation between the different points of the diagram and the table. As also shown in FIG. 4, the system according to the invention furthermore provides a torque management in avoidance, that is to say the system allows the limit current I _LIM to be exceeded in order to have a better response of the system to avoid an obstacle by a quick maneuver. The avoidance current I _EV is obtained from the limiting current I _LIM by multiplication according to a correction coefficient, as shown in the diagram fig 4 box 19b representing on the ordinate axis the current I and on the axis of abscissa the speed V, the speed of the vehicle V _VEH .

The manner in which the limiting current I _LIM is taken into account in the system proposed by the invention will be described below with reference to FIGS. 3 and 4. In FIGS. 3 and 4, the calculation of the maximum limiting current noted I _LIM is shown by box 19, FIG. 3 indicating that the calculation of the actual current limit is carried out at 19a, then corrected by the avoidance function at 19b. .

As shown in the diagram of the electro-pump unit 1 of FIG. 3, the computer 13 comprises a microprocessor 17 which is intended to establish by calculation the engine speed setpoint C _RPM , that is to say the setpoint of speed of rotation of the engine, from the vehicle speed V _VEH and the speed of rotation of the steering wheel V _VO and, also by calculation, the limit current I _LIM , from the vehicle speed V _VEH and representative values of the battery voltage U _BAT and of the temperature values T _mos of the active elements of electronic devices and the temperature T _ca of the card of this device. The calculation operations of the engine speed setpoint C _RPM and the limit current I _LIM are symbolized in the figure by boxes marked 18 and 19. The values of the battery voltage and of the temperature are applied to the inputs of a circuit of formatting 20 which adapts the level of these values to the level allowable for the microprocessor 17 which performs, before using them for calculating the current I _LIM in 21 a software formatting 21.

After calculating the motor speed set point C _RPM and the current I _LIM , the microprocessor 17 calculates the motor control C _M. This calculation is symbolized by box 22. The engine control C _M is sent to the engine after having been shaped by a circuit 23 of the computer. The calculation of the motor control C _M , carried out by the microprocessor 17, again takes into account the current I _M consumed by the motor, the value of which has been shaped by the circuit 24 of the computer and software formatted in FIG. by the microprocessor.

Figure 4 shows in more detail the implementation of the operations just described. As can be seen in this figure, the result of the calculation engine speed calculation performed at 18 is subjected to a decision logic symbolized by the box 27, which is intended to let the setpoint C _RPM for a servo operation of speed, materialized by block 28 or to prohibit this passage, according to a rotation authorization signal S _AR of binary nature, which is the result of an assessment of the speed of rotation of the motor V _RPM , provided for provide protection for the pump. This operation will be described in more detail below and is designated by the reference 30.

The speed control box 28 thus receives at an input a signal which is either the engine speed set point C _RPM equal to zero, as a function of the rotation authorization signal S _AR applied to box 27. The box speed control 28 receives at a second input a signal representative of the speed of rotation of the motor, noted V _RPM and produces at its output a signal S _PWM1 to ensure the nullity of the error between the two input signals , namely the setpoint C _RPM and the speed signal V _RPM . The signal is advantageously a pulse width modulated signal. The control is effected by applying the output signal S _PWM1 to a first input of a bit comparator 31 which receives at a second input the calculated current value I _LIM and to a third input the information of the motor current I _M. From the comparison operation results a signal S _PWM2 , which is either identical to the signal S _PWM1 or equal to zero, the signal is applied to a motor power control 32 applied to the motor 2.

The control loop formed by the speed control unit 28, the comparator 31, the motor power control 32 and the motor 2 is designed to ensure that the motor rotation speed V _RPM is slaved to the engine speed set point C _RPM which has been calculated in 22. As long as the consumed motor current I _M is less than the limit current value I _LIM , the comparator 31 passes the signal S _PWM1 to the motor control 32. When the current I _M is greater than the value of the limiting current I _LIM , the comparator prohibits the passage of the signal S _PWM1 , which has the consequence that the signal S _PWM2 becomes zero and the power control of the motor decreases until the current I _M consumed by the motor becomes lower than current I _LIM . This situation causes the comparator to allow again the passage of the signal S _PWM1 to the motor control 32.

As stated above, the invention provides a pump protection function in the case where the rotational speed of the motor 2 is too low to ensure proper operation of the pump. This protection function is illustrated by the diagram inside box 28 of FIG. 4 represents the speed of rotation V _RPM as a function of time t. When the speed of rotation has passed below a minimum speed threshold V _min , the engine is stopped after a time t1 and is then restarted after a time t2, the stopping and starting times t1 and t2 being fixed but configurable. It is also possible that the times t1 and t2 are modulated according to the accelerations and decelerations of the engine. In this case, the modulation laws of t1 and t2 are parameterizable. Depending on the state of rotation of the motor, the protection function 30 of the pump applies to the decision logic 27 of FIG. 4, the aforementioned authorization signal of rotation S _AR , which is of a binary nature and leads to the decision logic to allow the passage of the engine speed setpoint C _RPM to the speed control box 28, as described above, is prohibited this passage of the signal.

Figure 5 illustrates another version of implementation implementation of the strategy of the system according to the invention, which consists in replacing the comparator 29 of FIG. a scalar controller 34, the motor control 32 thus becoming a scalar command that can limit the torque supplied to the engine 2 by checking the value of the phase currents and by slaving the phase difference between the field created by the Bri diet and that Ba created by the magnets at a constant value of ± π / 2. This command is particularly known for synchronous machines in which the stator is generally provided with a three-phase winding, powered by a voltage and current system and creating in the gap a rotating induction field Bri. Field Bri tends to attract the rotor which is provided with magnets permanent generating an induction field Ba. As the rotor attracts the stator, the induction field tends to to align, thus giving birth to an electromagnetic couple.

FIG. 6 shows another version of implementation of the invention that provides a vector control of the motor and uses instead of the scalar controller 34 of FIG. 5 a vector controller 35. The vector control makes it possible to limit the torque supplied to the motor by directly controlling the current vector I _{s (t)} . As is known, all the information relating to the three currents of the three phases of the motor can be combined into a single mathematical quantity, namely the current phasor which is a spatial quantity. The advantage of using a spatial phaser rather than processing scalar magnitudes is that the three pieces of information relating to the three phase currents of the motor are combined into a single complex size.

The phasor represented by the vector current I in the diagram given inside the vector controller box 35 can be decomposed, in a two-phase space system equivalent to a three-phase scalar system, according to a direct stator current component I _D carried on the X-axis and a quadrature stator current component I _Q carried on the ordinate axis. The advantage lies mainly in handling only two quantities.

Of course, the invention which has just been described in referring to the figures, in its application to a vehicle to provide assistance to the management of this one is not limited to this application. This last has been indicated only as an example.

Indeed, the invention is usable in all cases where an electric pump unit is used which is intended for provide hydraulic power while providing for protection against possible overpressures in the hydraulic circuit, for example in braking and suspension of a motor vehicle or forklifts or the like.

Claims (8)

Electro-pump group system, of the type comprising an electric motor, a hydraulic pump driven by the electric motor and intended to provide hydraulic power to a hydraulic device, and means for limiting the pressure of the hydraulic fluid sent by the pump in the hydraulic circuit, characterized in that the means for limiting the pressure are in the form of electronic management means (13 ', 17, 15). System according to Claim 1, characterized in that the limitation of the pressure is effected by setting the maximum limiting current I _LIM to be sent to the motor (2) for driving the pump (3). System according to claim 2, of the type comprising a computer for managing the operation of the system, characterized in that the computer (13 ') is adapted to provide the aforementioned electronic management. System according to claim 3, characterized in that the computer (13 ') comprises means for calculating the maximum limiting current I _LIM to be sent to the motor (2) for driving the pump (3). System according to Claim 4, characterized in that the means for calculating the maximum limiting current I _LIM are adapted to ensure an increase in the maximum limit current by multiplication by a predetermined avoidance coefficient, for example of an obstacle when driving the vehicle. System according to Claim 5, characterized in that the electronic pressure limiting means are adapted to compare the motor current I _M with the maximum limiting current I _LIM and provides a control preventing the motor current I _{M from} exceeding the limit current I _LIM . System according to Claim 6, characterized in that the electronic management means are adapted to prevent the motor (2) from operating at low rotational speeds which can lead to inappropriate operation of the pump (3). System according to one of claims 1 to 7, characterized in that it is intended to equip a motor vehicle and provide assistance to the steering thereof, by means of a hydraulic cylinder device.

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