DE102023126073A1 - Method of pump operation, fluid pump and hydraulic device - Google Patents

Abstract

The invention relates to a method for pump operation (10) of an electrically operated fluid pump (12) for providing at least one fluid volume flow (Vf) of a fluid, comprising operating the fluid pump (12) with an electrical pump current (Ips) as a function of at least one manipulated variable (16), and initiating, in an emergency operating situation with the absence of the manipulated variable (16), an emergency operation (24) with operation of the fluid pump (12) at a predetermined target pump speed (nps) that is temperature-independent with respect to a fluid temperature (Tf) of the fluid, and limiting the pump current (Ips) to at most a first maximum current value (Ipmax1). The invention further relates to a fluid pump (12) and a hydraulic device.

Description

The invention relates to a method according to claim 1. Furthermore, the invention relates to a fluid pump and a hydraulic device.

In DE 10 2021 104 238 A1 A method for controlling a hydraulic device is described in which a pump speed of a fluid pump is preset for a switching process.

If the fluid pump is used to provide a fluid flow rate, for example, to cool a vehicle component, the pump speed is typically adjusted based on at least one control variable. If the control variable is missing in an emergency operation situation due to a fault, the fluid pump can no longer be operated reliably and precisely, and the cooling of the vehicle component may be inadequate.

The object of the present invention is to operate the fluid pump reliably and safely in an emergency operating situation. The vehicle component supplied by the fluid volume flow should be supplied with a sufficient fluid volume flow.

At least one of these objects is achieved by a method having the features of claim 1. This allows the fluid pump to be operated reliably and safely in an emergency operating situation. Overloading of the fluid pump can be prevented. The vehicle component can receive a sufficient fluid volume flow. The safety and reliability of the vehicle component are increased.

The fluid pump can be arranged in a vehicle. The vehicle can be a motor vehicle or a two-wheeled vehicle. The motor vehicle can be an electric vehicle.

The fluid pump may be a gear pump. The fluid pump may be designed as a reversing pump and, when rotating in a first direction of rotation, primarily provide a fluid pressure of the fluid and, when rotating in an opposite second direction of rotation, primarily provide a fluid volume flow, in particular for cooling and/or lubrication.

The fluid pump can be operated with a speed-controlled or speed-regulated control, particularly depending on the manipulated variable as the input variable. If the manipulated variable is missing in an emergency operation situation, the input variable for controlling (open-loop or closed-loop control) the fluid pump to adjust the pump speed can be missing. The manipulated variable can be an operating parameter, such as a temperature of the vehicle component, a fluid pressure of the fluid, and/or a fluid temperature of the fluid. The manipulated variable can be measured or calculated.

The emergency operation situation can arise if there is a fault in the electric motor and/or its electrical control, for example an inverter.

The pump current required to provide a given fluid volume flow at a given electrical pump voltage depends on the fluid temperature, particularly due to temperature influences of the fluid viscosity and temperature-dependent fluid pressure differences. With increased pressure differences on the inlet side (suction side) of the fluid pump, cavitation influences can also play a role. The required pump current for a given fluid volume flow increases nonlinearly with decreasing fluid temperature.

The first maximum pump current can be a maximum permissible continuous electrical current that the fluid pump and/or its control can withstand without impairment.

The fluid may be an oil, in particular a hydraulic oil.

During emergency operation, the fluid pump is operated without knowledge of the existing fluid temperature.

In a preferred embodiment of the invention, it is advantageous if the pump flow limitation is implemented independently of the fluid temperature. Preferably, the emergency operation is implemented independently of the fluid temperature. The fluid temperature during emergency operation can be below 0°C.

In an advantageous embodiment of the invention, the pump current is limited by directly specifying the first maximum current value. The first maximum current value can be determined depending on a predetermined maximum temperature, in particular of the fluid pump and/or the electrical control of the fluid pump.

A preferred embodiment of the invention is advantageous in which the limitation of the pump current is achieved by specifying a maximum electrical power value, from which a second maximum current value is calculated for a given electrical pump voltage and the pump current is limited to a maximum of the second maximum current value. The second maximum current value Ipmax2 can be calculated from the maximum power value and the pump voltage as follows $$Ipma\mathrm{<figure-callout\; id="2"\; label="x"\; filenames="DE102023126073A1\_0006.png"\; state="\{\{state\}\}">x</figure-callout>}2=\frac{Ppmax}{Up}$$

The second maximum current value can form the first maximum current value.

In a preferred embodiment of the invention, it is advantageous if the pump current is limited to the smaller of the two maximum current values (first maximum current value, second maximum current value). If the second maximum current value is smaller than the first maximum current value, the pump current can be limited to a maximum of the second maximum current value. If the first maximum current value is smaller than the second maximum current value, the pump current can be limited to a maximum of the first maximum current value.

In a preferred embodiment of the invention, the pump voltage is limited depending on the maximum power value. The maximum voltage value can be calculated as follows depending on the maximum power value and the first maximum current value: $$Upmax=\frac{Ppmax}{Ipmax1}$$

In a preferred embodiment of the invention, the target pump speed is predetermined depending on a minimum fluid volume flow. The minimum fluid volume flow can be between 1 and 10 liters, preferably between 2 and 6 liters per minute, particularly preferably between 2.5 and 4.5 liters per minute. The minimum fluid volume flow can be 3 liters per minute.

The target pump speed can be specified such that a minimum fluid volume flow is achieved. The minimum fluid volume flow can be the smallest possible fluid volume flow intended for cooling at least one vehicle component, in particular an electric motor. A fluid volume flow below the minimum fluid volume flow can no longer achieve sufficient cooling of the vehicle component.

In a specific embodiment of the invention, it is advantageous if, in emergency operation, limiting the pump current takes priority over maintaining the target pump speed. This can prevent electrical and thermal overload of the fluid pump and/or the electrical control of the fluid pump.

Furthermore, within the scope of the invention, a fluid pump having the features of claim 9 is proposed to solve at least one of the above-mentioned problems.

Furthermore, within the scope of the invention, to achieve at least one of the aforementioned objects, a hydraulic device with the features of claim 10 is proposed. The vehicle component can be an electric motor of the vehicle. The electric motor can generate a drive torque for propelling the vehicle. The electric motor can be arranged in an electric drive axle (E-axle) of the vehicle.

The hydraulic device may include at least one switching valve for controlling the fluid volume flow. The switching valve may be electrically actuated. The switching valve may be a solenoid valve.

The hydraulic device may include a fluid reservoir. The fluid pump may feed the fluid volume flow from the fluid reservoir. The fluid pump may be connected to a supply line from the fluid reservoir on the inlet side.

Further advantages and advantageous embodiments of the invention emerge from the description of the figures and the illustrations.

Character description

• 1: Ein Verfahren zum Pumpenbetrieb in einer speziellen Ausführungsform der Erfindung.
• 2: Ein Diagramm über einen Fluidvolumenstrom abhängig von einer Fluidtemperatur.

The invention is described in detail below with reference to the figures. They show in detail:

• 1 : A method for pump operation in a specific embodiment of the invention.
• 2 : A diagram of a fluid volume flow depending on a fluid temperature.

1 shows a method for pump operation in a specific embodiment of the invention. The method for pump operation 10 is applied to an electrically operated fluid pump 12 for providing at least one fluid volume flow Vf of a fluid. The fluid volume flow Vf may be required for cooling a vehicle component 14, in particular an electric motor, of a vehicle. In an emergency operating situation in which, for example, the electric motor and/or its control system has a fault, the fluid pump 12 should provide a minimum fluid volume flow Vfmin, in particular of approximately 3 liters per minute, in order to sufficiently cool the electric motor. Insufficient cooling can damage the electric motor and can lead to potential threat to vehicle safety.

The fluid volume flow Vf is provided by operating the fluid pump 12 as a function of at least one manipulated variable 16. Using the manipulated variable 16 as an input variable to a speed controller 18 of a pump speed of the fluid pump 12, a pump speed to be set is calculated, which is converted by a current controller 20 into an electrical pump current Ips of the fluid pump 12, with which the fluid pump 12 is to be operated. The pump current Ipa present at the fluid pump 12 is determined by a current determination 22 and returned to the current controller 20 as an input variable.

In an emergency operation situation with the absence of the manipulated variable 16, which represents the input variable for the speed control of the fluid pump 12, an emergency operation 24 is initiated with the fluid pump 12 operating at a predetermined target pump speed nps that is temperature-independent with respect to a fluid temperature Tf of the fluid and the pump current Ips is limited to a maximum of a first maximum current value Ipmax1. As a result, the fluid volume flow Vf provided by the target pump speed nps can ensure sufficient cooling of the electric motor, and the current limitation of the pump current Ips to the first maximum current value Ipmax1 can protect the control of the fluid pump 12 and/or the fluid pump 12 from electrical and thermal overload. The target pump speed nps is predetermined as a function of the minimum fluid volume flow Vfmin.

The emergency operation 24 is carried out independently of the temperature with respect to the fluid temperature Tf, i.e. even at a fluid temperature Tf below 0°C. The limitation of the pump current Ips is achieved by directly specifying the first maximum current value Ipmax1 on the one hand, but also by specifying an electrical maximum power value Ppmax on the other hand, from which a second maximum current value Ipmax2 is calculated by a current calculation 26 for a given electrical pump voltage Up.

The second maximum current value Ipmax2 can be calculated from the supply voltage, the input current and the pump voltage Up as follows $$Ipmax2=\frac{Ppmax}{Up}$$

The pump current is limited, alternatively or additionally, by the second maximum current value Ipmax2. Depending on which of the two maximum current values Ipmax1 or Ipmax2 is smaller, the pump current limitation Ips determines how high the pump current Ips can be at most.

Alternatively, the pump voltage Up can be limited to a maximum voltage value Upmax using the dashed connecting arrow shown here. The maximum voltage value Upmax can be calculated as follows, depending on the maximum power value Ppmax and the first maximum current value Ipmax1. $$Upmax=\frac{Ppmax}{Ipmax1}$$

2 shows a diagram of a fluid volume flow as a function of a fluid temperature. The fluid volume flow Vf provided by the fluid pump for cooling a vehicle component, such as the electric motor, is determined depending on the fluid temperature Tf of the fluid. As the fluid temperature Tf increases, the fluid volume flow 28 increases during normal operation of the fluid pump.

If an error occurs and an emergency operation situation is thereby initiated, the fluid pump is operated by an emergency operation in which the fluid pump can be operated at a predetermined target pump speed that is independent of the fluid temperature Tf of the fluid and thus provides the constant fluid volume flow 30.

Investigations have shown that this setting of a constant target pump speed is insufficient because at low fluid temperatures the electrical pump current can become excessive and lead to failure of the fluid pump or its control.

Therefore, in emergency mode, the fluid pump is operated not only at the temperature-independent specified target pump speed, but also with the pump current limited to the first maximum current value. This current limitation occurs particularly at fluid temperatures below 0°C, which is evident from the fluid volume flow 32 steadily increasing at low temperatures up to the minimum fluid volume flow.

Additionally or alternatively, the limitation of the pump current can include a specification of a maximum electrical power value, from which the second maximum current value is calculated and specified for a given pump voltage. This results in the fluid volume flow 34, which is between 0°C and -10°C up to the minimum fluid volume. lumen flow increases more slowly than if the pump current is directly limited by directly specifying the first maximum current value.

List of reference symbols

10

Pump operation procedures

12

Fluid pump

14

Vehicle component

16

Control variable

18

Speed control

20

Current control

22

Current determination

24

Emergency operation

26

Electricity calculation

28

Fluid volume flow

30

Fluid volume flow

32

Fluid volume flow

34

Fluid volume flow

IPA

applied pump current

Ipmax1

first maximum current value

Ipmax2

second maximum current value

IPS

Pump current

Ppmax

Maximum power value

Tf

Fluid temperature

Up

Pump voltage

Upmax

Maximum voltage value

Vf

Fluid volume flow

Vfmin

Minimum fluid volume flow

nps

Target pump speed

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 10 2021 104 238 A1 [0002]

Claims (10)

A method for pump operation (10) of an electrically operated fluid pump (12) for providing at least one fluid volume flow (Vf) of a fluid, comprising operating the fluid pump (12) with an electrical pump current (Ips) as a function of at least one manipulated variable (16), in an emergency operating situation with the absence of the manipulated variable (16), initiating an emergency operation (24) with operating the fluid pump (12) at a predetermined target pump speed (nps) that is temperature-independent with respect to a fluid temperature (Tf) of the fluid, and thereby limiting the pump current (Ips) to at most a first maximum current value (Ipmax1). Procedure according to Claim 1 , characterized in that the limitation of the pump flow (Ips) with respect to the fluid temperature (Tf) is carried out independently of the temperature. Method according to one of the Claims 1 until 2 , characterized in that the limitation of the pump current (Ips) is effected by directly specifying the first maximum current value (Ipmax1). Method according to one of the preceding claims, characterized in that the limitation of the pump current (Ips) is carried out by specifying an electrical maximum power value (Ppmax), from which, for a given electrical pump voltage (Up), a second maximum current value (Ipmax2) is calculated and the pump current (Ips) is limited to at most the second maximum current value (Ipmax2). Procedure according to Claim 4 , characterized in that the pump current (Ips) is limited to the smaller of the two maximum current values (Ipmax1, Ipmax2). Procedure according to Claim 4 or 5 , characterized in that the pump voltage (Up) is limited depending on the maximum power value (Ppmax). Method according to one of the preceding claims, characterized in that the target pump speed (nps) is predetermined as a function of a minimum fluid volume flow (Vfmin). Method according to one of the preceding claims, characterized in that in the emergency operation (24) the limitation of the pump current (Ips) takes priority over maintaining the target pump speed (nps). Fluid pump (12) for providing at least one fluid volume flow (Vf) of a fluid as a function of an electrical pump current (Ips), wherein the fluid pump (12) is configured to be operated by a method for pump operation (10) according to one of the preceding claims. Hydraulic device comprising a fluid pump (12) according to Claim 9 and a cooling device supplied by a fluid volume flow (Vf) of the fluid pump (12) for cooling a vehicle component (14) of a vehicle.

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