DE102018123085A1 - METHOD AND SYSTEM FOR COOLANT FLOW CONTROL FOR A DRIVE MACHINE IN A VEHICLE DRIVE SYSTEM - Google Patents

Abstract

A vehicle drive system includes a prime mover having a coolant inlet and a coolant outlet, a coolant flow controller having a flow control inlet in communication with the engine coolant outlet and a flow control outlet in communication with the engine coolant inlet, and a controller determining a coefficient based on engine power and which provides a coolant flow command signal to the coolant flow controller based on the power of the prime mover.

Description

TECHNICAL AREA

The present disclosure relates to a method and system for coolant flow control for a prime mover in a vehicle drive system.

INTRODUCTION

This introduction generally represents the context of the disclosure. The work of the present inventors in the scope described in this Background section, as well as aspects of the description that are otherwise not prior art at the time of application, are expressly implied in the present disclosure approved as state of the art.

Vehicle propulsion systems may control the engine coolant flow based on a predetermined set of gain coefficients determined by steady state operation of the prime mover in a variety of operating conditions and determining the optimum set of gain coefficients for each operating condition. For example, in an internal combustion engine having a valve-controlled flow of coolant, the engine may be operated at a selected speed and load and the proportional and integral gains for valve timing adjusting the flow of coolant to the engine are determined, resulting in an engine coolant exit temperature. which best follows a desired temperature. In this way, the gain factors for each engine speed and load can be calibrated and a table of the calibrated gains made for each individual engine speed and load.

In this calibration method, the gain factors can be optimized so that the response is not over or under attenuated. An overdamped system can lead to a coolant temperature that reacts very slowly. An under-damped system can lead to a coolant flow temperature that repeatedly exceeds and falls below the setpoint temperature and can generally be unstable. An underdamped system tends to overload the components of the coolant flow control system, which can lead to excessive wear and reduced life. Further, underdamped coolant temperature control may result in excessive temperature fluctuations that may adversely affect the components of the cooling system.

Using this system, the higher the number of operating conditions for which gain factors are determined to ensure optimal coolant flow control, the better. With the number of operating conditions for which optimal gain factors are determined in this way, however, inevitably increases the required calibration effort.

SUMMARY

In an exemplary aspect, a vehicle drive system includes a prime mover having a coolant inlet and a coolant outlet, a coolant flow controller having a flow control inlet in communication with the engine coolant outlet and a flow control outlet in communication with the engine engine coolant inlet, and a controller that provides a coefficient based on power of the prime mover and which provides a coolant flow command signal to the coolant flow controller based on the power of the prime mover.

In another exemplary aspect, the controller continues to determine the performance of the prime mover.

In another exemplary aspect, the system further includes a coefficient memory in association with the controller storing a table of coefficients each corresponding to a power of the prime mover, and wherein the controller determines the coefficient by looking up a coefficient from the table of coefficients corresponds to a power of the prime mover.

In another exemplary aspect, the coolant flow control includes a coolant flow control valve.

In another exemplary aspect, the coolant flow command signal includes a coolant flow control valve position command signal.

In another exemplary aspect, the coolant flow control includes a coolant pump.

In another exemplary aspect, the system further includes a temperature sensor that generates a temperature signal representative of a temperature associated with the prime mover.

In another exemplary aspect, the coolant flow command signal is based on a difference between the temperature signal and a predetermined setpoint temperature.

In this way, the selection of control system coefficients based on the power of the prime mover significantly improves the control of the temperature of an engine in a vehicle drive system, which in turn improves fuel economy, efficiency, performance, reliability and durability, vibrations and Reduces the temperature fluctuations of the actuators, improves the reactivity, reduces the thermal load and at the same time significantly reduces the workload associated with a calibration process that determines the coefficients corresponding to the performance of the engine.

Further fields of application of the present disclosure will become apparent from the following detailed description. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure.

The above features and advantages as well as other features and advantages of the invention will be readily apparent from the following detailed description, including the claims and the embodiments, when taken in conjunction with the accompanying drawings.

list of figures

• 1 ist eine schematische Darstellung einer exemplarischen Ausführungsform eines Wärmemanagementsystems 10 für ein Fahrzeugantriebssystem gemäß der vorliegenden Offenbarung;
• 2 ist eine schematische Darstellung einer weiteren exemplarischen Ausführungsform eines Wärmemanagementsystems 10 für ein Fahrzeugantriebssystem gemäß der vorliegenden Offenbarung;
• 3 ist eine Grafik zur Verdeutlichung des Zusammenhangs zwischen der Motorleistung und der optimierten Temperatursteuerungsverstärkung;
• 4A ist eine Grafik zur Verdeutlichung des Temperaturverhaltens eines Wärmemanagementsystems eines Fahrzeugs;
• 4B ist eine Grafik zur Verdeutlichung des Temperaturverhaltens eines Wärmemanagementsystems eines Fahrzeugs gemäß der einer exemplarischen Ausführungsform der vorliegenden Offenbarung; und
• 5 ist ein Flussdiagramm eines exemplarischen Verfahrens gemäß der vorliegenden Offenbarung.

The present disclosure will be better understood with the aid of the detailed description and the accompanying drawings, in which:

• 1 is a schematic representation of an exemplary embodiment of a thermal management system 10 for a vehicle drive system according to the present disclosure;
• 2 is a schematic representation of another exemplary embodiment of a thermal management system 10 for a vehicle drive system according to the present disclosure;
• 3 Fig. 12 is a graph for illustrating the relationship between the engine output and the optimized temperature control gain;
• 4A is a graph illustrating the temperature behavior of a thermal management system of a vehicle;
• 4B FIG. 4 is a graph illustrating the temperature behavior of a thermal management system of a vehicle according to an exemplary embodiment of the present disclosure; FIG. and
• 5 FIG. 10 is a flowchart of an exemplary method in accordance with the present disclosure. FIG.

DETAILED DESCRIPTION

The inventors have found that the thermal dynamics of a thermal management system for an internal combustion engine varies depending on the operating conditions. The gain coefficients, which may be optimal for a particular operating condition, may result in either over-oscillatory or under-average (slow) behavior under other operating conditions. To optimally control the temperature of this engine, therefore, the gain coefficients used should also change according to the changed operating conditions. As a result, monitoring and adjustment based on temperatures alone has not proven itself in changing operating conditions. However, the challenge was to find out which of the measurable operating conditions correlated most closely with the optimal gain coefficients. The inventors have found that a strong correlation between the power produced by a prime mover, such as a Internal combustion engine is generated, and there is the gain of the coefficients of a control that has been optimized to follow a target temperature exactly.

1 is a schematic representation of an exemplary embodiment of a thermal management system 10 for a vehicle drive system according to the present disclosure. The system 10 can be a prime mover 12 such as an internal combustion engine. The system 10 can continue via a coolant control valve 14 and a temperature sensor 16 feature. A coolant can be through the engine 12 to and from a coolant subsystem 18 , such as a heat exchanger, circulate. A controller 20 , such as an engine control module, having one or more look-up tables stored in an associated non-volatile memory 20a , receives a temperature signal from the temperature sensor 16 and a signal P, which is a power of the prime mover 12 represents one or more in the lookup table 20a to select stored coefficients to a command signal for controlling the coolant control valve 14 to create. The power signal P may be independent or separate from the controller 20 to be provided. Alternatively, the power signal P may be controlled by the controller 20 calculated or otherwise determined based on other signals (not shown) which the performance of the prime mover 12 can show. The control 20 can change the position of the valve 14 which in turn controls the coolant flow through the prime mover 12 controls.

2 is a schematic representation of another exemplary embodiment of a thermal management system 100 for a vehicle drive system according to the present disclosure. The thermal management system 100 includes a prime mover 102 , such as, without limitation, an internal combustion engine, engine, battery, or the like, which may be an energy source for propulsion of a vehicle in which the vehicle propulsion system is located. In the 1 schematically illustrated exemplary embodiment includes a prime mover 102 with a split cooling system. A split cooling system provides separate cooling paths for the engine block 104 , the head 106 and the exhaust manifold 108 for integration into the head 106 , A split cooling system can bring many benefits, such as selective control, which block 104 , the head 106 and / or the exhaust manifold 108 can be cooled. Typically, the head is pointing 106 a much lower mass than the block 104 , and in a first start condition, the head may 106 Heat much faster and must be cooled while the engine block 104 may not need to be refrigerated while the block 104 is further heated to the desired operating temperature. In this way, split cooling systems can be achieved by selectively controlling the cooling of block 104 , Head 106 and the exhaust manifold 108 offer several benefits, which in turn can help achieve optimal oil temperatures, improved combustion conditions, faster warm-up, improved fuel economy, efficiency, performance, and reduced emissions.

The thermal management system 100 can be a coolant pump 110 include a coolant flow to the engine 102 via an engine coolant inlet path 112 that provides with every block 104 , the head 106 and the exhaust manifold 108 can be in fluid communication. The system 100 can also be a first coolant control valve 114 in fluid communication with a coolant outlet 116 of the block 104 include. The first coolant control valve 114 can be selectively applied to the flow of coolant through the block 104 to control. The system 100 may further include a second coolant control valve 118 in fluid communication with a coolant outlet 120 the exhaust manifold 108 include. The second coolant control valve 118 can be selectively actuated to control the flow of coolant through the exhaust manifold 108 to control. Furthermore, the system can 110 a third coolant control valve 122 with an inlet connected to the outlet of the first coolant control valve 114 , the second coolant control valve 118 and an outlet 124 Of the head 106 is in fluid communication. That is, the third coolant control valve 122 receives all coolant flow from the engine 102 , The third coolant control valve 122 is selectively actuatable to determine the proportion of coolant flow that is a bypass flow path 126 and a heat exchange flow path 128 is supplied. The bypass flow path 126 allows fluid communication between the third coolant control valve 122 and the pump 110 , The heat exchange flow path 128 includes a heat exchanger 130 which exchanges heat with that through the heat exchange flow path 128 flowing coolant allows. In an exemplary embodiment, the heat exchanger 130 a cooler to deliver heat from the coolant to the ambient atmosphere. In further exemplary embodiments, the heat exchanger 130 without limitation an oil heat exchanger, a transfer heat exchanger, a heater and / or the like.

The thermal management system 100 may further include a first temperature sensor 132 for detecting a first temperature associated with the block 104 is assigned, a second temperature sensor 134 for detecting a second temperature, the head 106 is assigned, and a third temperature sensor 136 to the Capture a third temperature to the exhaust manifold 108 is assigned. In addition, the thermal management system 100 a controller (not shown for reasons of simplicity and clarity) included with each of the temperature sensors 132 . 134 and 136 as well as the valves 114 . 118 and 122 connected is. The controller can be adapted to receive temperature signals from each of the temperature sensors 132 . 134 and 136 to receive and, based on these signals, each of the valves 114 . 118 and 122 to selectively actuate the coolant flow through the engine 102 to control.

Based on each of the measured temperatures, the controller may selectively actuate the associated valves to control the flow of refrigerant through the split cooling system such that each of the measured temperatures approaches the respective setpoint temperatures. For example, the controller may use the block valve 114 so control that the temperature of the block temperature sensor 132 a set temperature for the block 104 follows. In an exemplary embodiment, the controller may control the shut-off valve 114 operate according to the following: $$dV=Kp\times T_{\text{error}}+Ki\times {\displaystyle {\int }_{t-1}^t{T}_{\text{error}}dt}$$

Where dV is the change in volume between the block and the remainder of the engine determined by the control, Kp is a proportional coefficient, T _{fault is} the temperature difference between the set temperature and the measured block temperature, and Ki is an integral coefficient. T _error can be determined by: $${\text{T}}_{\text{error}}={\text{T}}_{\text{Should}}-{\text{T}}_{\text{block}}$$

Where T is the desired _target or desired coolant temperature at the engine coolant inlet 120 and T _block the actual coolant temperature at the engine coolant inlet 120 is.

In this way, the thermal management system 100 the engine 102 control amount of heat dissipated by the relative proportions of these coolant flow by adjusting the valves 114 . 118 and 122 controls. These valves can be set with a closed loop that operates on the basis of a fault or difference between the setpoint and actual temperatures. The effectiveness of this thermal management system 100 however, is based on proportional and integral coefficients, which are determined by calibrating these coefficients under certain conditions. As these conditions change from these particular conditions, the coefficients that correspond to the optimized performance of the prime mover in new conditions also change. Any reduction in engine temperature control due to a change in operating conditions may have a negative impact on the fuel efficiency, economy, life, reliability, and performance of the engine. To cope with the changing conditions, several different sets of coefficients can be determined, each corresponding to a different set of operating conditions. For example, a set of coefficients may be determined by a calibration procedure for each of the various engine speeds and / or loads. However, the determination of these different sets of coefficients requires considerable effort for the calibration. In addition, the operating conditions of a prime mover can be very different, which makes it increasingly difficult to obtain a set of coefficients for the individual operating conditions. Any increase in the resolution of the operating conditions for which coefficients are determined requires a corresponding increase in the calibration effort to obtain these coefficients.

According to an exemplary embodiment of the present disclosure, the thermal management system can greatly enhance the ability to precisely control the engine temperature for a wide range of different operating conditions by reference to engine performance. The inventors have found that scaling the coefficients of the control system is possible by comparing engine performance over a wide range of operating conditions. In this way, the control system and method accurately and reliably controls the temperature of the prime mover to more closely follow a setpoint temperature. According to an exemplary embodiment, the coefficients of the control system may be continuously optimized over a variety of operating conditions based on drive power while avoiding high calibration effort.

3 is a graphic 200 to clarify the relationship between engine performance and optimized temperature control. The horizontal axis 202 represents the engine power and the vertical axis 204 the gain coefficient value. The rows of dots in the graph correspond to optimized ones gain coefficient 206 , which were derived experimentally by means of a calibration method. The pattern of calibration gains 206 in the graph can be considered a best-fit curve 208 following. The derivation follows for the equation that underlies this curve.

To further illustrate the relationships discovered by the inventors, the characteristics of an engine thermal management system can be described as follows: $$Q=m_{K\text{ü}Hlmittel}{C}_{p.K\text{ü}Hlmittel}\left(T_{Out}-T_{in}\right)$$

Where Q is the heat output of the engine to the coolant flowing through the engine, m _{coolant is} the mass flow of the coolant through the engine, C _{p, coolant is} the specific heat and the constant pressure of the coolant, Tout is the temperature of the coolant at the engine coolant outlet, and T is _in the temperature of the coolant at the engine coolant inlet. The control system and method may form a closed loop over the temperature of the coolant at the engine coolant outlet, where equation (1) may be rewritten as: $$T_{Out}=\frac{Q}{m_{K\text{ü}Hlmittel}{C}_{P.K\text{ü}Hlmittel}}+T_{in}$$

With current engine thermal management systems, the mass flow rate of the coolant through the engine may not be directly measurable. However, one can estimate the heat output of the engine, Q, as approximately proportional to engine power under steady state conditions: $$Q=F\left(P_{MOtOr}\right)\approx C\cdot P_{MOtOr}$$

By substituting in equation (2), the following is achieved: $$T_{Out}=\frac{C\cdot P_{MOtOr}}{m_{K\text{ü}Hlmittel}{C}_{p.K\text{ü}Hlmittel}}+T_{in}$$

Although the mass flow rate of the coolant through the engine can not be measured directly, a valve in the engine thermal management system may control the amount of coolant flowing through the engine. For example, the operating position of a valve can determine the proportion of coolant flowing through the engine: $$m_{K\text{ü}Hlmittel.MOtOr}=m_{K\text{ü}Hlmittel.System}\%Ventil$$

Where m is _{coolant, motor is} the mass flow of coolant through the engine (corresponding to the _coolant above), m _{coolant, system is} the mass flow of coolant flowing through the valve-associated thermal management system, and% valve is the relative opening percentage of the valve , % Valve can be measured directly in some systems and / or correspond to a valve control signal that controls the function of the valve. By substituting into equation (4) one obtains: $$T_{Out}=\frac{C\cdot P_{MOtOr}}{m_{K\text{ü}Hlmittel}\%Ventil{C}_{p.K\text{ü}Hlmittel}}+T_{in}$$

A closed loop control identifies the amount of change in% of valve required to eliminate the difference between the actual measured T _out and the desired setpoint temperature of the engine coolant. By taking the partial derivative of equation (6) with respect to the coolant flow through the engine by a forward equilibrium point, this relationship can be characterized as: $${\frac{\partial T_{Out}}{\partial \left(\%Ventil\right)}|}_{ff}=-\frac{C\cdot P_{MOtOr}}{{\left(\%Venti{l}_{ff}\right)}^2{m}_{K\text{ü}Hlmitte{l}_{ff}}{C}_{p.K\text{ü}Hlmittel}}$$

Where% Ventilff is the forward abstracted valve position and m _{ff coolant,} the forward motor current at a given operating condition.

The higher the magnitude of this partial derivative, the more sensitive is the engine temperature for changing the valve position and the less the change in valve position to eliminate a given temperature error and the lower the gain necessary to maintain stability while maintaining an acceptable temperature Reaction is required. In particular, it can be expected that the ideal proportional gain of a control is proportional to the negative inverse of the partial derivative: $$K_{P.ideal}\alpha -{\left(\frac{\partial T_{Out}}{\partial \left(\%Ventil\right)}\right)}^{-1}$$

The inventors have also understood that there is a relationship between the coolant flow, the nominal heat dissipation and thus the engine power and the setpoint temperatures. At the forward equilibrium point we get: $$C\cdot P_{MOtOr}=m_{K\text{ü}Hlmittel.ff}\%Valv{e}_{ff}{C}_{p.K\text{ü}Hlmittel}\left(T_{Out.SOll}-T_{in.Ziel}\right)$$

Where T _{out, Des is} the desired coolant temperature at the engine coolant outlet and T _{in, Des is} the desired coolant temperature at the engine coolant inlet. By substituting this into the partial derivative equation ( 8th ), repealing some terms and redesigning to simplify: $$\frac{\partial T_{Out}}{\partial \left(\%Ventil\right)}=\frac{m_{K\text{ü}Hlmitte{l}_{ff}}{C}_{p.K\text{ü}Hlmittel}{\left(T_{Out.Ziel}-T_{in.Ziel}\right)}^2}{C\cdot P_{MOtOr}}$$

Therefore, by deducing and understanding this relationship, the inventors have found that as the engine power increases, so too should the gain coefficient for temperature management control.

Based on this understanding, a set of gain coefficients may be developed and / or calibrated based on a power of the prime mover (ie, a single variable) selected and set forth in a table for use in a valve control in a prime mover temperature control system based on a single factor ( ie power of the prime mover). Compared to conventional calibration methods that develop a table of the gain coefficients of the control system based on different engine speeds and / or loads, the present disclosure greatly simplifies and reduces the calibration effort and further improves the control of the engine temperature by reducing the complexity and the coefficients identified different performances of the prime mover. This reduces the calibration task from two dimensions to a single dimension.

In this way, different operating conditions, which may have similar engine performance, have similar gain coefficients. The gain coefficients for a temperature control system for the prime mover of a vehicle may be planned based on the power of the prime mover.

While the previous description describes a temperature management system that integrates a valve that controls the proportion of coolant flow through the engine compared to the remainder of a larger system. It should be understood that in another exemplary embodiment, an internal combustion engine having a split cooling system may be used in which, for example, the coolant flow through the engine may be proportionally split between a block, head, and / or integrated exhaust manifold, and a shut-off valve is installed , which measures the amount of coolant flow through the block of the engine compared to the total flow of coolant through the engine, such as in FIG 1 illustrates, splits. In this exemplary embodiment, the temperature of the block may be accurately controlled by relating the mass flow rate of the coolant through the block to the total mass flow rate of the coolant through the engine, based on: $$m_{K\text{ü}Hlmittel.BlOck}=m_{K\text{ü}Hlmittel.MOtOr}\%BlOck$$

Where m is _{coolant, block is} the mass flow of coolant through the block, m is _{coolant, motor is} the mass flow of coolant through the engine, and% block is the relative position of the shut-off valve.

While the foregoing description has been provided with respect to the adjustment of a valve for controlling the flow of coolant through a thermal management system, it should be understood that other components of such a system that vary the flow of coolant may be similarly controlled. For example, rather than controlling the position of a valve, the control system and method of the present disclosure may be used to adjust the flow rate through a coolant pump.

In addition, the control system and method of the present disclosure rely on engine performance to determine which of a number of gain coefficients may be used in a vehicle thermal management system. Vehicle drive systems typically calculate the power of the prime mover, which is then available throughout the vehicle drive system for many purposes, such as in a vehicle thermal management system according to the present disclosure.

In an exemplary embodiment of the present disclosure, the controller may control the performance of the engine 102 determine. The jointly issued U.S. Patent No. 9,611,781 , the disclosure of which is incorporated herein in its entirety, discloses a method for determining the power of an engine. To determine the power of the engine, the operating speed of the engine may be detected, for example, by monitoring a signal from a crankshaft sensor, engine speed sensor, and / or the like. An engine speed sensor may monitor the engine speed and return a monitored engine speed result to the controller. For example, the controller may determine a maximum braking torque for the engine using the engine speed and one or more look-up tables, and then calculate the engine power from the maximum braking torque and the engine speed. In general, the controller may multiply the maximum braking torque by the engine speed to calculate the engine output. The calculated engine power may then be used by the controller with the equations described above to vary the gain coefficients used by the controller to control the valves in the thermal management system.

There may be other systems and methods for determining the performance of the prime mover that may also be used without limitation with an exemplary embodiment of the present disclosure. For example, an amount of fuel flowing into an internal combustion engine, the heat capacity of that fuel, and the combustion efficiency of the internal combustion engine may be used as a basis for selection from a coefficient table in a vehicle thermal management system. Alternatively, the crankshaft power may be a good indicator of combustion performance. And in a preferred exemplary embodiment, engine power may be related to crankshaft power and used to determine which coefficients are used in a vehicle thermal management system to control the temperature of the prime mover.

The 4A and 4B illustrate the improved response of an exemplary embodiment according to the present disclosure as compared to a conventional system. In 4A represents the line 300 the coolant temperature and the line 302 the position of a valve that controls a flow of coolant. 4A illustrates a subdued behavior of the coolant temperature 300 , The coefficients for the vehicle thermal management system that the in 4A illustrated results were determined and based on engine speed and / or load. When the valve opens and closes and / or changes position, the coolant temperature will fluctuate 300 and is not regulated very fast near a target temperature.

In clear contrast illustrated 4B a large improvement in the performance of a vehicle thermal management system according to an exemplary embodiment of the present invention Epiphany. The coolant temperature is through the line 304 and the position of a valve that controls the flow of coolant through the line 306 shown. Since the coefficients on which the vehicle thermal management system relies are derived from and based on engine power, the position of the valve settles 306 and the coolant temperature 304 much faster. The coolant temperature 304 approaches the setpoint temperature in 4B compared to 4A much faster and is set to this. This significantly reduces wear on the valve as the valve does not move as close as in 4A shown. In addition, performance, fuel efficiency, economy, reliability and life are significantly improved as the temperature is controlled much better by the thermal management system.

5 illustrates a flowchart 500 of a method for controlling a temperature in a vehicle thermal management system according to an exemplary embodiment of the present disclosure. The procedure begins at step 502 and go with step 504 continued. In step 504 the controller receives a power associated with a prime mover. For example, the controller may receive a predetermined power signal or alternatively calculate the power. The procedure then moves to step 506 The controller then refers to a look-up table of coefficients, each corresponding to a power, and determines which of the coefficients correspond to the power of the prime mover. That is, the controller seeks one or more coefficients from a look-up table based on the performance of the prime mover. The procedure then moves to step 508 continue, in which the controller receives a temperature signal and then moves to step 510 continued. In step 510 the controller compares the received temperature signal with a predetermined setpoint temperature to determine a temperature error signal. The procedure then moves to step 512 , wherein the control on a control algorithm, the detected temperature error signal and the in step 506 to look-up coefficients (or coefficients) to compute a command signal. In this way, the command signal is based not only on the temperature error, but also on the performance of the prime mover. The procedure then moves to step 514 wherein the command signal is received from a coolant flow controller, such as a coolant valve, a coolant pump, and / or the like, which is then responsive to the control of a coolant flow. The procedure then goes to step 516 over, the process ends.

This description is merely illustrative and is in no way intended to limit the present disclosure or its teachings or uses. The comprehensive lessons of disclosure can be implemented in many forms. Thus, while the present disclosure includes particular examples, the true scope of the disclosure is not in any way limited thereby, and further modifications will become apparent from a study of the drawings, the specification, and the following claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The 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

• US 9611781 [0047]

Claims (8)

A vehicle drive system comprising: an engine having a coolant inlet and a coolant outlet; a coolant flow controller having a flow control inlet in communication with the coolant outlet of the prime mover and a flow control outlet in communication with the coolant inlet of the prime mover; and a controller that determines a coefficient based on a power of the engine, and that provides the coolant flow controller with a command signal based on the power of the engine. System after Claim 1 wherein the controller further determines a power of the prime mover. System after Claim 1 and further comprising a coefficient memory in communication with the controller storing a table of coefficients each corresponding to a power of the engine, and wherein the controller determines the coefficient by looking up a coefficient from the table of the coefficients corresponding to a power of the engine. System after Claim 1 wherein the coolant flow control comprises a coolant flow control valve. System after Claim 4 wherein the coolant flow command signal comprises a coolant flow control valve position command signal. System after Claim 1 wherein the coolant flow control comprises a coolant pump. System after Claim 1 further comprising a temperature sensor that generates a temperature signal representing a temperature associated with the prime mover. System after Claim 7 wherein the coolant flow command signal is further based on a difference between the temperature signal and a predetermined target temperature.

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