Patent Application
20180135607
The invention concerns a method for operating a fluid delivery system, with a fluid delivery pump, a voltage manipulator, and an electric motor. The fluid delivery system is integrated into an electrical grid and the electric motor can be controlled by a voltage applied to the electric motor and the voltage manipulator is upstream from the electric motor.
Fuel delivery pumps are used in fuel delivery systems to convey fuel from the fuel tank to the combustion engine. Electrically powered fuel delivery pumps are used for delivery that have a pump module powered by an electric motor. The fuel delivery pumps must ensure the delivery of fuel over a wide operating range. For example, the fuel delivery pumps must provide a sufficient output at full throttle of the combustion engine as well as at low speeds or at a standstill of the motor vehicle.
On the one hand, the maximum possible output depends on the construction of the fuel delivery pump, whereby the maximum output also increases along with the size of the fuel delivery pump, and on the other hand, the maximum possible output depends on the rotational speed of the pump module, which is significantly determined by the level of electrical power. The maximum output therefore also depends directly on the supply voltage of the electric motor and the current strength supplied to the electric motor.
The electrical voltage available within the electric on-board system of a motor vehicle is regularly limited to a certain maximum level so that the voltage supplied to the fuel delivery pump cannot be arbitrarily increased and therefore, the maximum rotational speed is limited, thereby also limiting the maximum output.
In the most recent background art, apparatuses are known that provide an additional booster to increase the voltage to the fuel delivery pump. Thereby, for example, the booster is composed of an electric circuit consisting of a plurality of components.
A disadvantage of the apparatuses known from the most recent background art is particularly that an unfavorable power loss results in the electric system during operation due to the use of the booster that is particularly caused by the additional inductance of the booster and the power semiconductors used for the booster. Furthermore, the boosters are not optimally controlled to optimally compensate for the resulting disadvantages.
Therefore, it is an object of one aspect of the present invention to create a method that allows for optimized operation of a booster in order to increase the maximum output of a fuel delivery pump and, at the same time, to minimize the power loss resulting due to the booster.
An exemplary embodiment of one aspect of the invention concerns a method for operating a fluid delivery system, with a fluid delivery pump, a voltage manipulator, and an electric motor, wherein the fluid delivery system is integrated into an electrical grid and the electric motor can be controlled by a voltage applied to the electric motor and the voltage manipulator is upstream from the electric motor, wherein the following steps are performed:
A fluid delivery system can in particular be a fuel delivery system to convey fuel from a fuel tank to a combustion engine. In addition, applications in water or oil circuits are also possible, among other things.
A voltage manipulator is an electronic component that can affect the voltage. The voltage manipulator can be composed of a single component or a plurality of combined elements. The control of the voltage manipulator can take place, for example, via a control unit. So-called boosters can be used as voltage manipulators, which serve to amplify and/or attenuate electric signals. Here, only the voltage level itself can be changed or, for example, also the switching frequency of a signal. The voltage manipulator can be enabled to actively influence the voltage, thereby generating an increase or a reduction of the voltage, for example. As an alternative, by additionally activating the voltage manipulator, or instead of increasing and/or decreasing the voltage, another function can also be achieved. For example, the voltage manipulator can act as a filter for the switching frequencies in the electrical grid.
Using an electrical grid, switching from one or a plurality of components is intended, for example, from control units, energy sources, and actuators. For example, this can be composed of the on-board voltage grid of a motor vehicle. The electric motor of the fluid delivery system is connected to the electrical grid in such a way that its rotational speed can be regulated. The rotational speed of the electric motor, and therefore also the fluid delivery pump connected to the electric motor, is an important criterion for determining the fluid output of the fluid delivery pump. In order to convey a certain desired fluid output, a certain determinable rotational speed level of the fluid delivery pump is necessary. The desired rotational speed level can be achieved by applying a suitable voltage to the electric motor.
Preferably, the voltage manipulator is used to generate a suitable voltage level for the electric motor. This will ensure a sufficient fluid output.
The fuel delivery system can be controlled both by the applied voltage, as well as by pre-setting the rotational speed. Thereby, there is however a correlation between the applied voltage and the pre-set rotational speed of the fuel delivery pump, which is dependent on the respective fuel delivery system and the operating conditions at hand. Preferably, a voltage, which must be applied to the fuel delivery pump, is also determined for a fuel delivery system controlled via the rotational speed in order to reach the pre-set rotational speed.
It is especially beneficial if the voltage manipulator is activated when the voltage that is required to reach a rotational speed of the fluid delivery pump is outside a pre-defined voltage range.
The electrical grid is generally operated at a certain voltage level. The voltage that can be applied to the electric motor from the electrical grid is therefore limited. Therefore, the possible maximal rotational speed is also limited, since this directly depends on the voltage on the electric motor. Should a rotational speed be required to ensure the fluid output, which makes a voltage above the maximum voltage in the electrical grid necessary, this rotational speed cannot be reached without a change in the voltage. The voltage manipulator can suitably increase the voltage of the electrical grid to ultimately generate a voltage on the electric motor that exceeds the maximum voltage of the electrical grid. The voltage manipulator can thus act as a voltage amplifier.
In the opposite case, the voltage manipulator can also be used to lower the voltage to a level that cannot be supplied from the electrical grid. This is particularly beneficial to not have to reduce the voltage in the remaining electrical grid to an unnecessary extent, since other consumers require a higher voltage level for example. In this way, a very low voltage can be applied to the electric motor, which results in a very low rotational speed while the voltage in the remaining electrical grid remains practically unchanged.
In an application without a voltage manipulator, a reduction of the rotational speed can alternatively be achieved, for example, by reducing the modulation frequency of a pulse-width modulated signal used to control the electric motor. However, this is unfavorable since unfavorable acoustic effects can be caused by reducing the modulation frequency under a defined limit.
The pre-defined voltage range is preferably determined by the voltage level of the electrical grid.
A preferred exemplary embodiment is characterized in that the electrical grid is operated at a specifiable mains voltage, whereby the voltage, at which the electric motor is controlled, can be reduced to a level below the mains voltage by the voltage manipulator. This is beneficial for expanding the rotational speed range of the electric motor that is available, thereby enhancing the entire fluid delivery pump. Here, the voltage manipulator acts as a signal attenuator. This is particularly beneficial if the electrical grid is operated using a very high voltage that is either only temporarily limited or permanently applied to the electrical grid. For example, this is the case in an electric vehicle that regularly has a considerably higher mains voltage. Particularly during recuperation, meaning the recovery of electric energy from the motion of the electric vehicle, a very high voltage level can result in the electrical grid.
It must also be preferred if the electrical grid is operated at a specifiable mains voltage, whereby the voltage, at which the electric motor is controlled, can be increased to a level above the mains voltage by the voltage manipulator. Here the voltage manipulator acts as a signal amplifier that raises the voltage level of the signal with regard to the voltage level of the electrical grid, whereby a higher rotational speed can be generated on the electric motor and therefore also on the fluid delivery pump. By this, the range of applications of a fluid delivery pump can be expanded to a maximum level since the voltage amplification makes operation at a higher rotational speed possible. The rotational speed range of the electric motor and therefore the fluid delivery pump is expanded by this. With the aforementioned possibility of being able to reduce the voltage under the voltage level of the remaining electrical grid, thereby, overall, the rotational speed range is expanded both upwardly as well as downwardly.
Furthermore, it is beneficial if the voltage manipulator acts as a filter between the electric motor and the remaining electrical grid.
A filter is particularly favorable to keep differences, especially in the switching frequency of the signals used, separate from one another upstream and downstream from the voltage manipulator. For example, it is advantageous if the switching frequency in the remaining electrical grid is considerably higher than the switching frequency between the voltage manipulator and the electric motor. The remaining electrical grid can, for example, be operated at a switching frequency of approximately 500 kHz, whereby an attenuation or filtering of the electrical grid can take place using simpler elements and less effort than is the case with considerably lower switching frequencies. Nevertheless, the voltage manipulator can however be designed in such a way that the electric motor is controlled with a considerably lower switching frequency, which can be, for example, 20 kHz to 25 kHz. A simple separation of both switching frequency ranges can be achieved by the voltage manipulator.
Furthermore, it is advantageous if the fluid delivery system is decoupled from the remaining electrical grid by the voltage manipulator with regard to the switching frequency of the control signals, whereby a lower switching frequency is predominant between the voltage manipulator and the electric motor than between the electrical grid and the voltage manipulator. This is advantageous to enable a simple filtering and/or attenuation of the electrical grid while a control signal with a switching frequency, which has optimized to the furthest extent possible, can nevertheless be applied to the electric motor.
It is also useful if the voltage emitted by the voltage manipulator to the electric motor corresponds to the voltage in the remaining electrical grid, whereby the switching frequency between electric motor and voltage manipulator is different from the switching frequency in the remaining electrical grid. This is favorable to achieve a decoupling of the switching frequencies, even if the voltage level otherwise remains unchanged.
Furthermore, it is beneficial if the voltage manipulator acts as an attenuator between the switching frequency of the control signal of the electric motor and the switching frequency in the remaining electrical grid. An attenuating function of the voltage manipulator is beneficial in order to achieve an extensive decoupling of the branch downstream from the voltage manipulator and the remaining electrical grid.
Furthermore, it is useful if the voltage manipulator is composed of a booster, whereby the booster is constructed according to the ZETA principle or the SEPIC principle or the BUCK principle or the BOOST principle. These aforementioned principles are known from the most recent background art and represent suitable construction models for a voltage manipulator.
It is also preferable if the voltage generated by the voltage manipulator and guided to the electric motor exactly corresponds to the required voltage to achieve a certain rotational speed of the fluid delivery pump or to convey a desired fluid output. This is advantageous to enable energy-efficient operation of the fluid delivery system to the furthest extent possible.
By using a voltage manipulator, a smaller-sized fluid delivery pump can be used that has been, in particular, optimized with regard to energy. As a rule, this can be operated in a range that is optimal with regard to energy and, if required, can be increased to a higher rotational speed level using the voltage manipulator. The efficiency loss that is inevitably caused through the use of a voltage manipulator can be compensated for by operating the remaining electrical grid and, in particular, the power module upstream from the electric motor in a particularly optimal range, whereby, overall, more energy-efficient operation is possible.
Furthermore, it is useful if a power module for block commutation is arranged between the voltage manipulator and the electric motor, whereby the power module is operated with a duty cycle of 90% to 100% and the rotational speed of the electric motor is controlled by the voltage emitted by the voltage manipulator. Being especially preferred, the duty cycle on the power module is approximately 100%.
The block commutation of the electric motor is achieved via the power module, whereby, in particular, a brushless direct-current motor can be operated in a beneficial way. The power module can be operated with different duty degrees or duty cycles, whereby the duty cycle indicates the relationship between the pulse duration and the period duration of pulses that are emitted by the power module. To achieve optimum operation with regard to energy, it is advantageous if the duty cycle is as high as possible, ideally being at 100%. By operating with a duty cycle of 100%, in particular, the resulting power loss can be optimized by reducing it.
In an application without an upstream voltage manipulator, the rotational speed regulation of the electric motor can take place by varying the duty cycle in the power module. However, operating situations may occur that are unfavorable in terms of energy due to a low duty cycle, since a high level of power loss is created by the power module in this area. It is more advantageous to achieve an operation of the power module with a duty cycle that is the highest possible in order to keep the power loss caused by the power module as low as possible. Due to the upstream connection of a voltage manipulator, a variation of the electric motor rotational speed can also be achieved if the power module's duty cycle constantly remains high.
Due to the aforementioned decoupling of the remaining electrical grid from the path between the voltage manipulator and the electric motor, it is also particularly possible to operate the power module at a switching frequency that is different from the switching frequency of the remaining electrical grid. This is especially advantageous to be able to operate the power module as well as the rest of the electrical grid with an optimal switching frequency respectively.
Favorable further embodiments of the present invention are described in the subclaims and in the following figure descriptions.
In the following, the invention is explained in detail using exemplary embodiments taking the drawings into consideration. The drawings show:
The desired fluid output is determined in Block 2. This can happen, for example, via an appropriate sensor or by specification deriving from a control unit. In the case of a fuel delivery system, the fluid output within the motor control unit is precisely known on a regular basis and can be provided by this as a value.
In Block 3, a rotational speed is determined from the determined fluid output at which the fluid delivery pump must rotate in order to convey the appropriate amount of fluid. For this purpose, further values are additionally included such as, for example, the pressure in the fluid delivery system, the temperature of the fluid to be conveyed or the viscosity of the fluid to be conveyed. The properties of the fluid delivery system, which are determined by the respective constructional embodiment, can also flow into the determination of the rotational speed.
Block 4 serves to determine the voltage that is required to allow the electric motor powering the fluid delivery pump to rotate at the determined rotational speed. The rotational speed of electric motors can be determined, among other ways, in particular, by the variation of the voltage applied to the electric motors.
Finally, in Block 5, a voltage manipulator is activated that influences the voltage signal in its amplitude in such a way that an increase or decrease of voltage is achieved. This then results in an increase or decrease of the rotational speed of the electric motor. Being particularly advantageous, the voltage manipulator can also change the voltage to a value above or below the voltage introduced into it. In addition, by activating the voltage manipulator, only a change in the switching frequency of the voltage can be achieved without increasing or decreasing the amplitude in the process.
On the right of the voltage manipulator 7, an electrical path 9 is shown, via which the voltage manipulator 7 is electrically conductively connected to a power module 10. The power module 10 serves to provide block commutation of the voltage and the voltage signal emitted by the voltage manipulator 7. A brushless direct-current motor can be powered by block commutation for example.
A filter 11 is arranged between the voltage manipulator 7 and the power module 10, which serves to filter the voltage emitted by the voltage manipulator 7.
Preferably, the voltage manipulator 7 is a so-called booster that is composed of a circuit consisting of a plurality of electrical and/or electronic elements. The booster can be constructed according to the various principles known from the most recent background art.
It is particularly advantageous if a frequency decoupling between the remaining electrical grid indicated on the left and the path 9 between the voltage manipulator 7 and the electric motor 8 can also be achieved by the voltage manipulator 7. The path 9 to the electric motor 8 is preferably operated at a switching frequency of approximately 20 kHz while the remaining electrical grid is operated at a considerably higher switching frequency of 500 kHz for example.
Another filter is shown with the reference number 12 that makes filtering of the voltages and voltage signals coming from the remaining electrical grid possible prior to reaching the voltage manipulator 7.
In particular, the exemplary embodiments in
Thus, while there have shown and described and pointed out fundamental novel features of the invention as applied to a preferred embodiment thereof, it will be understood that various omissions and substitutions and changes in the form and details of the devices illustrated, and in their operation, may be made by those skilled in the art without departing from the spirit of the invention. For example, it is expressly intended that all combinations of those elements and/or method steps which perform substantially the same function in substantially the same way to achieve the same results are within the scope of the invention. Moreover, it should be recognized that structures and/or elements and/or method steps shown and/or described in connection with any disclosed form or embodiment of the invention may be incorporated in any other disclosed or described or suggested form or embodiment as a general matter of design choice. It is the intention, therefore, to be limited only as indicated by the scope of the claims appended hereto.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2015 208 680.1 | May 2015 | DE | national |
This is a U.S. national stage of application No. PCT/EP2016/060373, filed on May 10, 2016. Priority is claimed on German Application No. DE102015208680.1, filed May 11, 2015, the content of which is incorporated here by reference.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2016/060373 | 5/10/2016 | WO | 00 |
