Patent Publication Number: US-2017370274-A1

Title: Coolant pump with integrated closed-loop control

Description:
The present invention relates to a coolant pump for pumping a coolant for an internal combustion engine in a vehicle comprising the internal combustion engine and a central engine control unit. 
     Developments have been made with a view to designing the thermal management of internal combustion engines so as to be more efficient, in order to reduce fuel consumption and emissions by vehicles. To this end, coolant pumps have been developed which facilitate a reliable and continuous adjustment of the volume flow of the circulating coolant. In order to keep the internal combustion engine in an optimum temperature range for efficient combustion and minimal exhaust emissions, the heat output of the cooling system is controlled depending on the current operating state. During a cold start phase, for example, heat output is prevented, initially altogether, and subsequently in part. 
     In the field of mechanically driven coolant pumps, with which a rotation of the internal combustion engine is transferred to a pump shaft via a belt drive, coolant pumps comprising an electro-hydraulically controlled regulating slide valve for adjusting the volume flow proved to be particularly reliable in the course of these developments. A pump of this design, which is now referred to as an ECF (electro-hydraulically controlled flow) pump, is disclosed for example in the German patent specification DE 10 2008 026 218 B4 of the applicant. 
     With such a coolant pump, a cylindrical regulating slide valve is moved by way of a hydraulic actuator around a peripheral region of an impeller of the coolant pump. In this case the hydraulic pressure of the actuator is not produced as result of a closed circuit with hydraulic oil; rather, it is applied via an auxiliary flow of the coolant. Pumps with such a coolant-based hydraulic system do not require additional dynamic seals against the atmosphere and have proved successful owing to their long service lives and the reliable control thereof. 
     The volume flow of the coolant to be pumped from a coolant pump is customarily controlled by a central engine control unit ZMS of a vehicle. In the case of a known coolant pump, a position of the regulating slide valve is detected for this purpose and transferred to the central engine control unit ZMS. The central engine control unit ZMS controls an electromagnetic valve in the hydraulic circuit depending on further operating parameters such as the speed of the internal combustion engine, the working load of the combustion engine, the amount of fuel supplied, the temperature and the like. 
     Depending on the number of parameters to be determined and the number of measuring elements necessary for this as well as the number of actuators to be controlled, a corresponding number of electric cables from the central engine control unit ZMS to the individual elements of the control circuit is required. In order to install an ECF pump, at least two cables must be installed for the power supply and for the signal communication both from the central engine control unit ZMS to the position sensor and from the central engine control unit ZMS to the electromagnetic valve. 
     The invention is based on the object of providing a coolant pump which requires minimal effort in terms of installation and which provides a high degree of operational reliability in a corrosive environment. 
     According to the invention, this object is achieved by a coolant pump with the features of claim  1 . 
     This coolant pump is particularly characterised by the fact that it comprises its own pump control which controls a proportional valve in a hydraulic circuit on the basis of the actual value signal from the sensor and a desired value signal from the central engine control unit. 
     The invention therefore provides for the first time in the design of coolant pumps a dedicated control circuit for the position control of a regulating slide valve using a hydraulic actuator. 
     The coolant pump according to the invention therefore comprises fewer electric cables to the central engine control unit than a conventional system. In particular, there is no need for a separate power supply or communication interface between both the central engine control unit ZMS and the electromagnetic proportional valve and the central engine control unit ZMS and a sensor for determining a parameter (such as the position of the regulating slide valve) which is indicative of the volume flow of the pumped coolant. 
     Just one power supply cable and one communication cable to the central engine control unit ZMS are required in the case of the coolant pump according to the invention. The fact that fewer cables and plug connections are required simplifies the design and reduces the manufacturing cost of the coolant pump as well as the cost of installing it in the vehicle. 
     Moreover, the coolant pump&#39;s susceptibility to failure can also be improved, since there is no need for corrodible plug connections and/or outlet seals on the pump housing for the wiring in the region of the engine compartment of the vehicle, which is exposed to the effects of the weather and stirred up grit. 
     The central engine control unit does not require a programming procedure for position controlling the regulating slide valve either. As a consequence, the processing load of the central engine control unit can be reduced. Thus, either a central engine control unit with lower processing power at a corresponding lower cost can be used or the unused processing power can be made available for control functions of other peripheral devices, or to achieve an increased frequency of calculation cycles. 
     Advantageous embodiments of the coolant pump according to the invention are described in the dependent claims. 
     In one advantageous embodiment of the invention, the pump control and the sensor can be formed as a single electronic component. As a result of the integration into one electronic component, external wiring to different regions of the pump construction can be dispensed with. The installation of the coolant pump can thereby be simplified and there is no need for corrodible plug connections and/or outlet seals on the pump housing for the wiring. 
     In a further embodiment of the present invention, the sensor can be a position sensor, in particular a Hall effect sensor, for detecting the position of the regulating slide valve. In this case, the desired value signal indicates a predetermined position of the regulating slide valve or a predetermined volume flow and the speed of the combustion engine or coolant pump. 
     If the desired value signal from the central engine control unit and the actual value signal from the position sensor each indicate a positional value of the regulating slide valve, the position control can be implemented in the pump control with a simple calculation procedure. The calculating capacity of the pump control as well as the power required and resulting waste heat in an enclosed electronic component can thereby be kept to a minimum. 
     If the desired value signal from the central engine control unit indicates a predetermined volume flow and a speed, a calculation procedure is performed by the pump control between the volume flow and the position of the regulating slide valve to be controlled depending on the pump speed. As a result, there is no need for a specific calculation based on individual parameters of the coolant pump by the central engine control unit. The central engine control unit then only transfers as a desired value signal a value corresponding to a volume flow, i.e. an amount of heat to be dissipated. The required heat output can be calculated by the central engine control unit on the basis of the operating parameters of the internal combustion engine. In this way, good compatibility and interchangeability between the coolant pump according to the invention and various central engine control units can be ensured. 
     According to one embodiment of the present invention, in the upper speed range of the pump the pump control can limit the path of the regulating slide valve. As a result, the pump control performs a protective function for components such as seals in the cooling system, in order to limit a maximum volume flow and the resulting pressure. 
     Moreover, according to one embodiment of the present invention, the pump control can compare the relationship between the control duration of the proportional valve and a resulting position change of the regulating slide valve with a threshold value. In this way, the pump control carries out autonomous function monitoring to ensure the cooling system has a sufficient fill quantity of coolant. 
     Since in this case the hydraulic circuit is used as a pressure-sensitive sensor, function monitoring can be implemented in the cooling system to ensure the timely detection of leaks without the need for further measuring elements, such as pressure gauges or other sensors, to be provided. This means that the number of components and wires as well as the costs and outlay involved in installation can be kept to a minimum. 
     In an alternative embodiment of the present invention, the sensor can be a pressure sensor for detecting the pressure of the pumped volume flow of the coolant. In this case, the desired value signal indicates a predetermined volume flow or a pressure which is indicative of the volume flow of the pumped coolant. The pressure sensor can preferably detect a pressure in the pump chamber which is in proportion to the pumped volume flow of the coolant pump. 
     According to one embodiment of the present invention, the pump control can compare the pressure detected by the sensor with a threshold value. In this way, it is possible for the pump control of the alternative embodiment to carry out with particular ease autonomous function monitoring with a pressure sensor, to ensure the cooling system has a sufficient fill quantity of coolant. 
     Function monitoring to ensure the timely detection of leaks can also be implemented with this embodiment without the need for further measuring elements to be provided in the cooling system, as a consequence of which the number of components and wires as well as the costs and outlay involved in installation can be kept to a minimum. 
     According to one embodiment of the present invention, the pump control can comprise a transceiver for receiving data from the central engine control unit and/or for sending data thereto, a microcomputer for performing a control procedure, a valve driver for controlling the proportional valve, and a power supply distributor for supplying each component with electric power. With this configuration, a control circuit of the pump control with small dimensions and advantageous installation possibilities in the coolant pump can be realised. 
     According to one embodiment of the present invention, the pump control can have a housing of its own which is integrated into the single electronic component. With this design, effective protection against electromagnetic interference from the control circuit to the sensor disposed in the electronic component, such as a Hall effect sensor, can be provided, for example. 
     According to one embodiment of the present invention, the sensor can have a housing of its own which is integrated into the single electronic component  20 . With this design too, effective protection can be provided against electromagnetic interference from the control circuit to the sensor. 
     According to one embodiment of the present invention, the coolant to be pumped can flow through a coolant inlet such that it is directed axially at the impeller and can be pumped by the impeller so as to leave the pump chamber via a radial coolant outlet. The invention therefore makes use of the configuration of a radial pump. 
     According to one embodiment of the present invention, the coolant to be pumped can flow through a coolant inlet such that it is directed axially at the impeller and can be pumped by the impeller so as to leave the pump chamber via an axial or semi-axial coolant outlet on the opposite side of the impeller. The invention therefore makes use of the configuration of an axial or a semi-axial pump. 
     An electronic component according to the invention for use in a mechanically driven coolant pump of a vehicle with an internal combustion engine and a central engine control unit comprises a pump control and a sensor for detecting the position of a regulating slide valve in a pump chamber which limits the pumped volume flow or a sensor for detecting the pressure of the volume flow in the pump chamber. The electronics required for the control can therefore be integrated with, exchanged for or retrofitted with a component in the coolant pump. 
     According to one embodiment of the present invention, a portion of the electronic component in which the pump control is accommodated and a portion of the electronic component in which the sensor is accommodated can form an L-shaped arrangement with respect to one another. With this embodiment, advantageous integration with the pump design as well as improved protection against interference between the control circuit and the sensor is ensured. 
     A method according to the invention for controlling a mechanically driven coolant pump of a vehicle with an internal combustion engine and a central engine control unit comprises the following steps: calculating by way of the central engine control unit the desired value of a parameter, which is indicative of the volume flow of the pumped coolant, depending on operating parameters of the internal combustion engine; transmitting the desired value from the central engine control unit to a pump control of the coolant pump; detecting the actual value of the parameter by a sensor; transmitting the actual value from the sensor to the pump control; and adjusting by way of the pump control the position of a regulating slide valve, which limits the pumped volume flow of the coolant pump, depending on the desired value and the actual value by controlling a hydraulic actuator. In this way, the invention makes use of a coolant pump of the aforementioned embodiments. 
     An alternative method according to the invention for controlling a mechanically driven coolant pump of a vehicle with an internal combustion engine and a central engine control unit comprises the following steps: transmitting operating parameters of the internal combustion engine from the central engine control unit to a pump control of the coolant pump; calculating by way of the pump control a desired value of a parameter, which is indicative of the volume flow of the pumped coolant, depending on the operating parameters of the internal combustion engine; detecting an actual value of the parameter by a sensor; transmitting the actual value from the sensor to the pump control; and adjusting by way of the pump control the position of a regulating slide valve, which limits the pumped volume flow of the coolant pump, depending on the desired value and the actual value by controlling a hydraulic actuator. In this alternative way, the invention makes use of a coolant pump of the aforementioned embodiments. 
     According to one embodiment of the present invention, the parameter which is indicative of the volume flow of the pumped coolant can be a position of the regulating slide valve. This makes it possible to use the control method for the configuration described above of the coolant pump according to the invention. 
     According to one embodiment of the present invention, the parameter which is indicative of the volume flow of the pumped coolant can be the pressure in a pump chamber of the coolant pump which corresponds to the volume flow of the pumped coolant. This makes it possible to use the control method for an alternative embodiment of the coolant pump according to the invention. 
    
    
     
       The invention will now be explained by way of an example embodiment with reference to the Figures in which: 
         FIG. 1  is a schematic sectional view of an inner region of the coolant pump and of wiring of the pump control according to the present invention; 
         FIG. 2  is a sectional view of a configuration of a coolant pump with a pump control according to the present invention, which is equipped with a plug for connection with a data bus; 
         FIG. 3A  is a sectional view of an electronic component into which a position sensor and a pump control according to the present invention are integrated; 
         FIG. 3B  shows a perspective view of an electronic component into which a position sensor and a pump control according to the present invention are integrated; 
         FIG. 4  shows a schematic block diagram of the pump control according to the present invention. 
     
    
    
     An exemplary configuration of the coolant pump will now be described with reference to  FIGS. 1 and 2 . 
     The coolant pump comprises a pump housing  1  and a pump shaft  4  which is rotatably mounted therein and which includes a pulley  3  driven by an internal combustion engine (not shown) through a belt drive. An impeller  5 , which is disposed inside a pump chamber  2  in a flow area of a cooling circuit of the internal combustion engine to induce a volume flow of the coolant, is non-rotatably arranged at a free end of the pump shaft  4 . The coolant is drawn through an axial inlet of the pump chamber  2  in the region of a central radius of the impeller  5  and is ejected, for example, through a radial outlet (not shown) of the pump chamber  2  which is opposite to a peripheral region of the impeller  5 . 
     The flow area of the impeller  5  can be variably covered along a displacement path extending in parallel to the pump shaft  4  by a regulating slide valve  7  with a cylindrical portion  7   a  arranged coaxially to the pump shaft and a back wall portion  7   b . A sealing lip  6  extends between the inner peripheral wall of the cylindrical portion  7   a  of the regulating slide valve  7  and a rear wall of the pump chamber  2 . In  FIGS. 1 and 2 , the regulating slide valve  7  is in an “open position” in which the flow area of the impeller  5  is not covered. 
     The pump chamber  2  also has arranged therein an axial piston pump  9  on the back side of the impeller  5  and in parallel to the pump shaft  4 , the piston of which is actuated via a sliding block which slides on a wobble plate  8  arranged on the rear side of the impeller  5  so as not to rotate therewith relative to the pump shaft  4 . 
     The axial piston pump  9  draws coolant from the flow area in the pump chamber  2  between the impeller  5  and the regulating slide valve  7  and ejects the coolant under pressure into a hydraulic circuit  11  formed in the pump housing  1 . The hydraulic circuit  11  branches out into two branches  11   a  and  11   b . The one branch  11   a  of the hydraulic circuit  11  leads, on the one hand, to an electromagnetic proportional valve  13  and back again into the pumped coolant flow. The other branch  11   b  of the hydraulic circuit  11  leads to an annular piston  15  which is arranged coaxially with respect to the pump shaft  4  and which assumes the function of a hydraulic actuator along the displacement path of the regulating slide valve  7 . 
     A return spring  17  acts upon the annular piston  15  in a direction opposite to the pressure of the hydraulic circuit  11 , i.e. away from the impeller  5 . The annular piston  15  communicates with the regulating slide valve  7  and moves this toward the impeller  5  as the pressure of the hydraulic circuit  11  increases. 
     One exemplary function for adjusting the volume flow of the coolant pump will now be described. 
     When no drive current is supplied, the electromagnetic proportional valve  13  is open such that the coolant drawn by the axial piston pump  9  flows substantially without pressure via the branch  11   a  of the hydraulic circuit  11  and through the proportional valve  13  back into the pumped coolant flow. Therefore, no pressure builds up in the branch  11   b  of the hydraulic circuit  11 , and the annular piston  15  remains in the unactuated initial position under the action of the return spring  17 . In this case, the regulating slide valve  7 , which communicates with the annular piston  15 , is kept in the “open position”, as is shown in  FIGS. 1 and 2 . 
     In the “open position” of the regulating slide valve, a maximum pumped volume flow is generated, regardless of the pump speed, without shielding of a flow-effective area of the impeller  5  by the regulating slide valve  7 . This state at the same represents a fail-safe mode to the effect that maximum volume flow and maximum heat output of the internal combustion engine are automatically ensured in the event of a power supply failure or a control defect, i.e. a deenergized electromagnetic proportional valve  13 . 
     When the electromagnetic proportional valve  13  is temporarily closed as a result of time-controlled supply of a drive current, the coolant ejected by the axial piston pump  9  cannot flow back into the volume flow via the branch  11   a  of the hydraulic circuit  11 . The pressure applied by the axial piston pump  9  in the hydraulic circuit  11  spreads from the backpressure at the closed proportional valve  13  into the branch  11   b  via the branch  11   a  and acts upon the annular piston  15 . The annular piston  15  moves the regulating slide valve  7  towards the impeller against the force of the return spring  17 . In this process, the cylindrical portion  7   a  of the regulating slide valve  7  is increasingly caused to axially overlap the impeller  5 , as a consequence of which an effective flow area of the impeller  5  is radially covered by the cylindrical portion  7   a  of the regulating slide valve  7 . 
     In the “closed position” of the regulating slide valve  7 , the cylindrical portion  7   a  completely covers the impeller  5  such that a minimal pumped volume flow is generated regardless of the pump speed in that a flow-effective area of the impeller  5  is completely shielded by the regulating slide valve  7 . 
     Controlling the on and off periods of the electromagnetic proportional valve  13  gives rise to the controlled build-up of backpressure in the branch  11   a , and thus to the controlled build-up of pressure in the branch  11   b  of the hydraulic circuit  11 , which acts upon the annular piston  15  and against the return spring  17 . The annular piston  15  moves the regulating slide valve  7  between the “open position” and “closed position” as described above, to adjust the pumped volume flow of the coolant pump. 
     The central engine control unit ZMS calculates the volume flow of the coolant to be pumped, which corresponds to the required heat output of the internal combustion engine, by taking account of various operating parameters such as the speed and working load of the internal combustion engine, the fuel supplied, the temperature, the vehicle speed, and the like. 
     As has been described above, the volume flow of coolant pumped by the coolant pump depends, on the one hand, on the flow effectiveness of the impeller  5 , which decreases around the impeller  5  with an increasing degree of coverage by the cylindrical portion  7   a  of the regulating slide valve  7  as the position of the regulating slide valve  7  (and of the annular piston  15 ) is, to an increasing extent, axially shifted towards the “closed position”. 
     On the other hand, the pumped volume flow of the coolant pump depends on the pump speed. The pump speed is invariably dictated by the speed of the internal combustion engine as a result of the belt drive and includes the fluctuations characteristic of vehicle operation. 
     An exemplary configuration of the pump control  21  will now be described with reference to  FIG. 4 . 
     In one example embodiment, the pump control  21  comprises a transceiver  23 , such as a LIN transceiver, a microcomputer  25 , a valve driver  27  and a power supply distributor  29 . The power supply distributor divides the voltage from a vehicle power source (not shown), such as 12V, into suitable voltages of the electronic components  23 ,  25 ,  27  of the pump control  21  and supplies these with the required electric power. The LIN transceiver  23  enables data communication via a data bus, e.g. in the UN protocol, between the pump control  21  and the central engine control unit ZMS. As is shown in  FIG. 2 , a plug  22  can be provided for connection with an on-board data bus linked to the central engine control unit ZMS. The microcomputer  25  carries out a control program with a control procedure which is stored in a memory (not shown) of the microcomputer  25 , and calculates a pulse width modulation as the drive signal of the valve driver  27 . The valve driver  27  amplifies the drive signal from the microcomputer  25  by activating and deactivating, in accordance with the pulse width modulation, the supply of power from the power supply distributor  29  for actuating the electromagnetic proportional valve  13 . 
     In one example embodiment shown in  FIGS. 3A and 3B , the pump control  21  is formed together with a sensor  19  as a single electronic component  20 . For example, a control circuit of the pump control  21  and a sensor circuit can be cast into one enclosed component. Insofar as the dimensions of the single component of the pump control  21  and sensor  19  do not exceed the dimensions of a conventionally used sensor component, it is moreover possible to upgrade a known ECF pump without modifying the pump construction. 
     The shown configuration can be preferably implemented using a Hall effect sensor as the position sensor  19 . However, this embodiment is not limited to a Hall effect sensor, as will be described later in a further embodiment. 
     In one embodiment of the coolant pump shown in  FIG. 1 , a position sensor  19  is used to detect the position of the regulating slide valve  7  along a displacement path. A contactless and robust construction is provided by a Hall effect sensor and a magnetic transmitter element which is connected to the annular piston  15 . The position sensor  19  outputs to the pump control  21  as an actual value signal the detected position of the annular piston  15 , and accordingly of the regulating slide valve  7 , along the displacement path. 
     In one example embodiment, the desired value signal which is received by the pump control  21  from the central engine control unit ZMS contains a predetermined position of the regulating slide valve  7 . To this end, the central engine control unit ZMS calculates the volume flow of the coolant to be pumped by the coolant pump on the basis of the required heat output of the internal combustion engine. The predetermined position of the regulating slide valve is then calculated depending on the volume flow and the current pump speed, which has a fixed speed ratio relative to the internal combustion engine, and is transmitted to the pump control  21 . 
     In a further preferred embodiment, the desired value signal which is received by the pump control  21  from the central engine control unit ZMS contains just one desired value for the required volume flow of coolant as well as further operating parameters such as, in particular, the current speed of the internal combustion engine or the corresponding pump speed. In this embodiment, the desired value for the resulting position of the regulating slide valve  7  is calculated in the pump control  21 . 
     The control procedure executed in the microcomputer  25  corresponds, for example, to the control function of a PID member with which a deviation is calculated between the predefined desired value and the actual value. Based on this deviation, a pulse width modulation for controlling the electromagnetic proportional valve  13  is calculated on the basis of a system-specific function of the hydraulic circuit  11 , i.e. a response behaviour between the on and off periods of the electromagnetic proportional valve  13  and a resulting position change of the annular piston  15  as a hydraulic actuator. 
     In order to retain the position of the regulating slide valve  7 , the pressure in the hydraulic circuit  11  is controlled by means of the on and off periods for opening and closing the proportional valve  13  in such a way that an equilibrium corresponding to the predefined desired value of the central engine control unit ZMS is achieved and maintained between the hydraulic pressure and the pressure of the return spring  17  at the position of the annular piston  15  and the regulating slide valve  7 . The actual position of the regulating slide valve  7  is detected by the position sensor  19  and transmitted to the pump control  21  or entered into the microcomputer  25  as feedback for controlling the proportional valve  13 . 
     According to a further example embodiment, the pump control  21  carries out function monitoring to autonomously identify and report to the central engine control unit leaks in the cooling system. 
     If air has become trapped in the coolant circuit as a result of leaks, it will also enter the hydraulic circuit  11  of the coolant pump and reduce the pressure in the hydraulic actuator. The characteristic curve of the return spring  17  which counteracts the annular piston  15  remains unchanged. The disequilibrium between the reduced hydraulic pressure and the unchanged characteristic curve of the return spring  17  must in this case be compensated by increasing the ratio of the on period to the off period of the electromagnetic proportional valve  13  so as to produce the hydraulic pressure for the desired position of the annular piston  15 . 
     The simple control loop between the position sensor  19  of the regulating slide valve  7  and the electromagnetic proportional valve  13  in the hydraulic circuit  11  allows the pump control  21  according to the invention to detect deviations in the response behaviour of the hydraulic circuit with the required sensitivity, i.e. particularly without being influenced by further operating parameters such as permanent speed and temperature fluctuations. The pump control  21  compares a deviation from the ratio between the on and off periods of the electromagnetic proportional valve  13  and the resulting position change of the annular piston  15  and regulating slide valve  7  with a threshold value stored in the memory. The threshold value is stored in a memory portion of the pump control  21 , as are other specific parameters of the coolant pump. 
     If an error is detected, the pump control  21  outputs an error message to the central engine control unit which can, in turn, initiate limited emergency operation or switch off the internal combustion engine. 
     In an alternative example embodiment, the coolant pump comprises a pressure sensor (not shown), which is preferably arranged between the annular piston  15  and the regulating slide valve  7 , instead of the position sensor  19 . 
     In this alternative embodiment, the pump control  21  carries out control in that the regulating slide valve  7  is moved into a new position so as to adjust the volume flow until the actual value signal of the pressure detected by the pressure sensor corresponds to the pressure of the predetermined volume flow, which is predefined by the desired value signal from the central engine control unit. 
     In this embodiment, function monitoring of the cooling system can be performed based simply on the existing pressure sensor rather than on the response behaviour of the hydraulic actuator. As has been described with regard to the previous embodiment, a threshold value is stored in a memory portion of the pump control. This threshold value corresponds to a minimal operating pressure which is particularly undershot when air becomes trapped in the cooling system. After comparing the desired value with the value detected by the pressure sensor, the pump control  21  evaluates whether there is a leak in the cooling system. 
     If an error is detected, the pump control  21  outputs an error message to the central engine control unit which can, in turn, initiate limited emergency operation or switch off the internal combustion engine. 
     In a modified embodiment, it is also possible to use an electric motor actuated proportional valve  13  instead of the electromagnetic proportional valve  13 . In this case, the drive signal for a servomotor does not need to contain a pulse width modulation. 
     It is furthermore possible to provide a CAN interface instead of a LIN interface between the pump control  21  and the central engine control unit ZMS.