CN111670352A

CN111670352A - Method for regulating the temperature of a coolant circuit of a drive unit on a test bench

Info

Publication number: CN111670352A
Application number: CN201980011120.2A
Authority: CN
Inventors: H·格鲁贝尔; M·蒙斯舍因; G·格里塞尔
Original assignee: AVL List GmbH
Current assignee: AVL List GmbH
Priority date: 2018-01-31
Filing date: 2019-01-31
Publication date: 2020-09-15
Anticipated expiration: 2039-01-31
Also published as: DE112019000295A5; CN111670352B; WO2019149792A1; AT520814A4; AT520814B1

Abstract

If the temperature difference is determined by the inlet temperature (Tin) of the coolant in the coolant inlet (9) and the return temperature (T) of the coolant in the coolant return (10)_out) The temperature difference (Delta T) between them is used to calculate the actual cooling power (P) prevailing in the coolant circuit (7)_cool，act) And using the regulator (R) to calculate the actual cooling power (P)_cool，act) With a predetermined theoretical cooling power (P)_cool，set) To calculate a control variable (ST) for a pretreatment unit (5) for the coolant in order to control the inlet circuitTemperature (T)_in) A test run on the test stand (1) can be achieved which is closer to the actual test run using the drive unit with the coolant circuit (7).

Description

Method for regulating the temperature of a coolant circuit of a drive unit on a test bench

Technical Field

The invention relates to a method for regulating the temperature of a coolant circuit of a drive unit on a test stand, and to a corresponding test stand, having a pretreatment unit for the coolant, wherein the pretreatment unit is connected to a coolant inlet of the coolant circuit and to a coolant return of the coolant circuit, and the pretreatment unit is used to set the inlet temperature of the coolant in the coolant inlet.

Background

It is known to operate an internal combustion engine on a test stand for development or testing purposes. The internal combustion engine can be built on the test stand (motor test stand) alone or in combination with other components of the vehicle in which the internal combustion engine is to be used. One example of this is a drivetrain test stand on which a drivetrain of a vehicle (also as a hybrid drivetrain) or a part having an internal combustion engine therein is operated with the internal combustion engine. However, the electric motor can also be used as the sole drive unit for operating the test stand alone or in combination with the drive train. A complete vehicle with a drive unit (internal combustion engine, electric motor or a combination of internal combustion engine and electric motor) can be arranged on the roller test stand. One or more load machines connected to the drive unit are also always arranged on the test stand, in order to be able to operate the drive unit on the test stand counter to the load.

Modern internal combustion engines are usually cooled with a coolant, which circulates through the internal combustion engine and a cooling device. The same applies to the case where the electric motor is part of or as a drive unit of a vehicle. Other coolant circuits (also with different coolants), such as charge air coolers, can also be provided on the internal combustion engine. For this purpose, a plurality of cooling devices, for example additional low-temperature cooling devices for the charge air cooling device, may also be provided. The circulation of the coolant is performed using, for example, a coolant pump driven by the internal combustion engine. In a practical vehicle, the cooling device, or cooling devices in a plurality of cooling cycles, is cooled by the driving wind, i.e. by the movement of the vehicle on the road. This is of course not possible on a test bench.

In general, the drive unit is also operated without a cooling device on the test stand, so that a coolant circuit of the drive unit needs to be implemented on the test stand in another way. Of course, this problem can also occur in vehicles on roller test stands, where there is likewise no driving wind. In this application, it is also necessary to implement the coolant circuit of the drive unit on the test stand in another way if the driving wind is not generated by a blower on the test stand.

Therefore, a pretreatment system for the coolant of the coolant circuit is often used on the test bench in order to keep the coolant at a defined temperature. In this case, a constant temperature of the coolant is usually set, which is sufficient for most applications. However, this is of course not satisfactory for simulating the actual travel of the vehicle on a test stand, since in an actual vehicle the constant temperature of the coolant is not adjusted during the actual travel on the road. In a vehicle, the temperature of the coolant is derived from the actual driving conditions (e.g. vehicle speed, driving route) and environmental conditions (e.g. ambient temperature) as well as from the characteristics of the operating states of the coolant pump and the drive unit (e.g. rotational speed, torque) and from the characteristics of the cooling device (e.g. cooling area, aerodynamics). The actual cooling power derived therefrom is therefore a complex function of these dependencies and cannot be simply calculated or simulated. Therefore, simulating the near-actual state of the cooling system of the drive unit on the test bench is a difficult task.

For example, EP 2573538 a2 describes a pretreatment system for cooling water for an internal combustion engine on a test bench. The pretreatment system is connected to a coolant circuit of the internal combustion engine in order to pretreat the coolant of the internal combustion engine. The preprocessing system therefore imitates the cooling device in the vehicle and should be adjusted in such a way that the actual driving behavior is achieved. However, in EP 2573538 a2 there is no mention of how this is done.

Disclosure of Invention

It is therefore an object of the present invention to provide a method for regulating the temperature of a coolant circuit of a drive unit on a test stand with a pretreatment unit for the coolant, and a test stand having such a pretreatment device.

According to the invention, said object is achieved by: the actual cooling power prevailing in the coolant circuit is calculated from the temperature difference between the inlet temperature of the coolant in the coolant inlet and the return temperature of the coolant in the coolant return, and the control variable for the pretreatment unit is calculated from the deviation between the calculated actual cooling power and a predefined setpoint cooling power by means of the controller in order to set the inlet temperature. This enables a very simple adjustment, which is arranged directly on the basis of the temperature difference which can be detected very simply. At the same time, this solution also makes it possible to achieve a very precise adjustment of the cooling power, which in turn makes it possible to bring the situation on the test stand close to the situation in which the actual driving is carried out with a vehicle having an internal combustion engine and a cooling device for cooling the coolant.

In an advantageous, easily implementable embodiment, the actual cooling power is formulated using a formula

Calculating, including mass flow through the coolant circuit

And known specific heat capacity c of the coolant_p. Together with this, a varying mass flow is taken into account. Since the coolant pump is usually driven by the internal combustion engine, the coolant pump does not provide a constant mass flow. However, the mass flow of course decisively influences the cooling performance. Thereby, the test bed can be usedAnd the test operation closer to the actual test operation is realized.

The regulation can be simplified if the temperature difference change to be set is first determined from the deviation between the calculated actual cooling capacity and the predefined setpoint cooling capacity and a set variable for the pretreatment unit is calculated therefrom. The temperature difference change can be formulated in a simple manner

And (4) calculating.

If the setpoint cooling capacity is obtained from a predetermined cooling device model, the actual performance of the actual cooling device in the vehicle can be simulated more precisely on the test bench by the preprocessing unit. The cooling device model can be obtained, for example, from measurements in the wind tunnel on the cooling device or from flow-technical and/or thermodynamic simulations.

Drawings

The solution according to the invention is explained in more detail below with reference to the accompanying figures 1 and 2, which show, by way of example, schematically and without limitation, advantageous embodiments of the invention.

In the figure:

FIG. 1 shows a test bench with a thermostat for a coolant according to the invention, and

FIG. 2 shows the determination of the theoretical cooling capacity for the cooling circuit of the thermostat

An embodiment of the present invention.

Detailed Description

Fig. 1 shows a typical test stand 1 with an internal combustion engine as a drive unit 2. The drive unit 2 may, however, also be an electric motor or a combination of an internal combustion engine and an electric motor (hybrid). The drive unit 2 can also be a component of the drive train or a part of the drive train. The drive unit 2 is connected to a load device 3, typically an electric motor, via a test stand shaft 4 to form a test apparatus. In order to carry out the desired test run on the test stand 1 using the drive unit 2, a test stand automation unit 6 is provided, which is dependent on the control variablesS_D、S_EThe drive unit 2 and the load machine 3 are adjusted according to the predetermination of the test run. During the test operation, certain measured values, typically emission or consumption values, power values, etc., of the drive unit 2 or the drive train are usually measured in a measurement-related manner, in order to be able to draw certain conclusions about the drive unit 2 therefrom.

The test operation is present, for example, as a temporal profile of the rotational speed and the torque of the drive unit 2. However, it is also possible to simulate the driving in a known manner, for example, in the test stand automation unit 6 using a virtual vehicle with a drive unit along a virtual driving route in order to obtain the control variables S required for controlling the drive unit 2 and the load machine 3 as a test run at each time_D、S_E. For the simulation, models such as a vehicle model, a tire model, a road model, a driver model, etc., are used, which are integrated in order to simulate a virtual driving. The required variables, for example the rotational speed and the torque of the drive unit 2, are then determined from the simulation within a predetermined time step. Such simulation and simulation models are known and available.

The measuring sensors can also be used on test stand 1 to detect the required measured variables, for example the rotational speed of drive unit 2 and/or load machine 3 and/or the torque of test stand shaft 4, which can be used for simulation and/or for regulating drive unit 2 and/or load machine 3. The drive unit 2 is regulated, for example, in such a way that, for each time step of the regulation, the accelerator pedal position or another suitable manipulated variable of the drive unit 2, which is derived, for example, from a predetermined torque request from a test run, is transmitted to the drive control unit 2. During each time step of the regulation, the load machine 3 can be predefined for a rotational speed to be set, which is set by a dinoteur regulator (dynaregler) on the test stand 1. Of course, other adjustments of the test device on the test stand 1 are also possible and known. Since the test stand 1 and the manner and method of setting up and carrying out the test runs on the test stand 1 are not subject of the invention and are not essential to the invention, they are not discussed in detail here.

The drive unit 2 has at least one coolant circuit 7 with a coolant inlet 9, a coolant return 10 and a coolant pump 8 which is usually driven by the drive unit 2 itself. The coolant pump 8 may be arranged in the coolant inlet 9 or in the coolant return 10 and the coolant circulates through the drive unit 2, for example through a cooling circuit of the drive unit 2 or through a charge air cooling device of the internal combustion engine as the drive unit 2. The coolant is guided on the test stand 1 through a pretreatment unit 5, in which the inlet temperature T of the coolant in the coolant inlet 9 is set_in. In an actual vehicle, a cooling device for the coolant is provided in place of the preprocessing unit 5. Return temperature T of the coolant in the coolant return 10_outThis is obtained by operating the drive unit 2.

At return temperature T_outAnd the temperature T of the route_inSaid temperature difference Δ T ═ T between_out-T_inThe actual situation in the vehicle should be as close as possible to the test stand 1 in order to be able to carry out a test run on the test rig on the test stand 1 which is closer to the actual situation.

The pre-processing unit 5 is regulated by a control unit 11 (hardware and/or software) in which a regulator R (typically software) is implemented. The purpose of regulating the pretreatment unit 5 is to adjust the cooling effect of the coolant circuit on the drive unit 2 during the test run according to a certain predetermined value. For this purpose, the control unit 11 is predefined, for example by the test stand automation unit 6, with a setpoint value SW for cooling, for example a setpoint cooling capacity P described below_{cool_set}. During the implementation of the test operation or during the simulation of the simulated test run, the setpoint value SW for the cooling is again present, for example, as a temporal profile for the test operation, but may also be present by means of a cooling model, which is also in the form of a characteristic map. Such a characteristic map can be measured, for example, in the air duct, for example, as a function of the vehicle speed and the ambient temperature for the cooling power. Mathematical cooling device can also be trained from such measurementsAnd (5) placing a model. The cooling device model can also be obtained from flow technology and/or thermodynamic simulations.

For adjusting the pre-treatment unit 5, the cooling power P used is determined_coolTo proceed with. The cooling power is known from the relational formula

Results therein, including the temperature difference Δ T, the mass flow through the coolant circuit 7

And known specific heat capacity c of the coolant_p. However, in principle for calculating the cooling power P_coolOther schemes of (4) are also possible. The mass flow

For example, it can be measured directly with a mass flow sensor or a volume flow sensor, can be provided by the coolant pump 8 or can be derived from a measured variable of the coolant pump 8, for example the rotational speed of the coolant pump 8. Of course, volume flows can likewise be used in an equivalent manner

The volumetric flow is through a known density and mass flow of coolant

And (4) associating. Therefore, in order to adjust the return temperature T_outIn the case of (2) adjusting the desired approach temperature T_inSaid cooling power P must be applied by the pre-treatment unit 5_cool。

Current cooling power P_cool，actThe actual variable, the route temperature T, measured in a computing unit 12 (hardware and/or software), for example in a control unit 11, preferably according to the above formula, as the actual value IW for the regulation of the preprocessing unit 5_inTemperature T of return path_outAnd mass flow

To calculate. Adjusting the pre-treatment unit 5 by a predetermined theoretical cooling power P_cool，_actAs the theoretical value SW. The regulator R is controlled by the theoretical cooling power P_cool，setAnd the actual cooling power P_cool，actThe difference between these values is calculated as a function of the implemented control rule, for example a PI or PID controller, for the manipulated variable ST of the preprocessing unit 5, which is set in the preprocessing unit 5 by means of an actuator provided for passing through the route temperature T_inCauses the desired temperature difference change Δ T_DAnd thus causes a cooling power P_coolA change in (c).

It can also be provided here that the theoretical cooling power P is used_cool，setAnd the actual cooling power P_cool，_actThe difference between them, for example in the regulator R or in the computing unit 12, is first of all formulated

To calculate the required temperature difference change deltat_DThe regulator R thus determines the manipulated variable ST in order to use the preprocessing unit 5 to determine the temperature T of the route_inTo adjust for the desired temperature difference change deltat_D。

At the return temperature T of the coolant_outAfter the operation of the drive unit 2, the cooling power P according to the invention_coolIs essentially adapted to the purpose of regulating the inlet temperature T in the coolant inlet 9_inBut to the preprocessing unit 5.

Which adjustment variable ST is calculated in order to adjust the inlet temperature T in the preprocessing unit 5 in the desired manner_inOf course in relation to the embodiment of the pre-treatment unit 5. In the case of the pretreatment unit 5 as described in EP 2573538 a2, the manipulated variable ST is, for example, the valve position of a directional control valve. The manipulated variable can also control a heat exchanger as the pretreatment unit 5. Furthermore, there are of course also other possibilities, as the pretreatment unit 5 can be used, for example, as a conditioner with thermoelectric modules as described in WO 2016/207153A 1The temperature unit is implemented, which may also depend on other regulating variables. However, the specific embodiment of the preprocessing unit 5 and thus of the adjustment parameter ST is not a solution of the invention. In the sense of the present invention, the pretreatment unit 5 only has to be suitable for adjusting the temperature of the medium, in particular of the coolant, by means of the predetermined adjustment variable ST.

An advantageous embodiment of the invention is shown in fig. 2. In the test stand automation unit 6, a simulation unit 20 (hardware and/or software) is provided, in which simulation unit 20 a simulation model SM is implemented in order to simulate the travel of the vehicle with the drive unit 2 along a virtual route. In order to carry out a test on test stand 1, control variables S for load machine 3 are obtained from the simulation on test stand 1_DFor example, the rotational speed to be set and the control variable S for the drive unit 2_EFor example, the torque to be set or the accelerator pedal position. Furthermore, the cooling device model 21 (as hardware and/or software), for example as a characteristic map, is implemented in the test stand automation unit 6. The cooling device model 21 determines a setpoint value SW for setting the pretreatment unit 5, for example a setpoint cooling capacity P of the cooling device, from the determined input variables_cool，_set. In the illustrated embodiment, the cooling device model 21 is determined, for example, from a simulated vehicle speed V_VAnd the ambient temperature T_amb(which may be derived from the simulation or predetermined) to determine the cooling power P of the cooling device in the simulated vehicle_cool. For this purpose, the input variables for the cooling device model 21 can also be obtained by the simulation unit 20.

Claims

1. Method for regulating the temperature of a coolant circuit (7) of a drive unit (2) on a test stand (1) having a pretreatment unit (5) for the coolant, wherein the pretreatment unit (5) is connected to a coolant inlet (9) of the coolant circuit (7) and to a coolant return (10) of the coolant circuit (7), and the inlet temperature (T) of the coolant in the coolant inlet (9) is set using the pretreatment unit (5)_in) Characterised by the presence of a coolantTemperature (T) of coolant in the path (9)_in) With the return temperature (T) of the coolant in the coolant return (10)_out) The temperature difference (Delta T) between them is used to calculate the actual cooling power (P) prevailing in the coolant circuit (7)_cool，act) And using the regulator (R) to calculate the actual cooling power (P)_cool，act) With a predetermined theoretical cooling power (P)_cool，set) To calculate an adjustment variable (ST) for the preprocessing unit (5) in order to adjust the inlet temperature (T)_in)。

2. A method according to claim 1, characterized by using a formula

Calculating the actual cooling power (P)_cool，act) Including mass flow through the coolant circuit (7)

And known specific heat capacity c of the coolant_p。

3. Method according to claim 1, characterized in that the actual cooling power (P) is calculated from the measured values_cool，act) With a predetermined theoretical cooling power (P)_cool，set) The deviation therebetween determines the temperature difference change (Δ T) to be set_D) And the control variable (ST) for the preprocessing unit (5) is calculated therefrom.

4. A method according to claim 3, characterized in that it is according to the formula

Calculating the temperature difference change (Δ T)_D)。

5. Method according to one of claims 1 to 4, characterized in that the theoretical cooling power (P) is obtained from a predetermined cooling device model (21)_cool,set)。

6. Test stand having a drive unit (2) which is connected to a load machine, wherein the drive unit (2) comprises a coolant circuit (7) having a coolant, and a pretreatment unit (5) is arranged on the test stand (1) in order to set the temperature of the coolant circuit (7), wherein a coolant feed (9) and a coolant return (10) of the coolant circuit (7) are connected to the pretreatment unit (5), and the pretreatment unit (5) sets the feed temperature (T) of the coolant in the coolant feed (9)_in) Characterized by a control unit (11) of the pretreatment unit (5) which is determined from the inlet temperature (T) of the coolant in the coolant inlet (9)_in) With the return temperature (T) of the coolant in the coolant return (10)_out) The temperature difference (Delta T) between them is used to calculate the actual cooling power (P) prevailing in the coolant circuit (7)_cool，act) And a regulator (R) is provided, which is controlled by the actual cooling power (P) calculated_cool，act) With a predetermined theoretical cooling power (P)_cool，set) To calculate an adjustment variable (ST) for the preprocessing unit (5) in order to adjust the inlet temperature (T)_in)。

7. Test bench according to claim 6, characterized in that the control unit (11) is programmed to determine the actual cooling power (P) calculated from the measured values_cool，set) With a predetermined theoretical cooling power (P)_cool，_act) The deviation therebetween determines the temperature difference change (Δ T) to be set_D) And the adjustment variables (ST) for the preprocessing unit (5) are calculated therefrom.