Patent Document

FIELD OF THE INVENTION 
     The present invention relates to variable nozzle turbos (VNTs), and more particularly to a VNT solenoid temperature estimator. 
     BACKGROUND OF THE INVENTION 
     Internal combustion engines combust an air and fuel mixture within cylinders of the engine to produce drive torque. Engines can include a turbocharger that increases torque output by delivering additional air into the cylinders. One traditional turbocharger includes a variable nozzle turbo (VNT). VNT&#39;s include variable position vanes that regulate the amount of air delivered through the VNT. The vane position ranges from a fully-open position to a fully-closed position. In the fully-open position, the VNT delivers a minimum amount of air to the engine. In the fully-closed position, the VNT delivers a maximum amount of air to the engine. The vanes can be positioned between the fully-open and fully-closed positions to provide an intermediate amount of air to the engine. A vane solenoid adjusts the vane position based on a control signal and a vane position sensor generates a signal indicating the actual vane position for feedback control. 
     In general engine components, such as the vane solenoid, are affected by temperature. Traditionally, temperature sensors are incorporated at or near critical engine components to monitor temperature. In components such as VNTs, including a temperature sensor increases cost (e.g., cost of the sensor itself, wiring, packaging, etc.) and complexity. Further, because such components normally do not include temperature sensors, temperature based diagnostics and/or remedial actions are not included in traditional engine control systems. 
     SUMMARY OF THE INVENTION 
     Accordingly, the present invention provides a turbo system including a solenoid that is regulated based on a current signal to adjust an output of the turbo system. A driver module generates the current signal. The current signal is based on a commanded duty cycle signal, a voltage signal and an effective electrical impedance of the solenoid. A temperature estimator module estimates a temperature of the solenoid based on the current signal, the voltage signal and the commanded duty cycle signal. 
     In one feature, the turbo system further includes a voltage reading module that generates the voltage signal based on a voltage supply to the turbo system. 
     In another feature, the turbo system further includes a current reading module that measures the current signal. 
     In another feature, the turbo system further includes a filter that filters the voltage signal prior to processing of the voltage signal by the temperature estimator module. 
     In another feature, the turbo system further includes a filter that filters the duty cycle signal prior to processing of the duty cycle signal by the temperature estimator module. 
     In another feature, the turbo system further includes a filter that filters the current signal prior to processing of the current signal by the temperature estimator module. 
     In still another feature, the temperature estimator module implements a look-up table to determine the temperature. 
     In an alternative feature to the look-up table, the temperature estimator module can implement a multi-variable equation to determine the temperature. 
     Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a schematic illustration of a vehicle engine system including a variable nozzle turbo (VNT) according to the present invention; 
         FIG. 2  is a block diagram schematically illustrating a lab-based solenoid driver system that is used to create a solenoid temperature estimator according to the present invention; 
         FIG. 3  is a flowchart illustrating steps of creating the solenoid estimator according to the present invention; 
         FIG. 4  is a block diagram schematically illustrating a vehicle-based solenoid driver that provides signals to the solenoid temperature estimator; and 
         FIG. 5  is a flowchart illustrating a vehicle control method based on an solenoid temperature estimate. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, the term module refers to an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, or other suitable components that provide the described functionality. 
     Referring now to  FIG. 1 , an exemplary engine system  10  is schematically illustrated in accordance with the present invention. The engine system  10  includes an engine  12 , an intake manifold  14 , a fuel injection system  16  and a turbocharger  18 . The exemplary engine  12  includes six cylinders  20  configured in adjacent cylinder banks  22 , 24  in V-type layout. Although  FIG. 1  depicts six cylinders (N=6), it can be appreciated that the engine  12  may include additional or fewer cylinders  20 . For example, engines having 2, 4, 5, 8, 10, 12 and 16 cylinders are contemplated. It is also anticipated that the engine  12  can have an inline-type cylinder configuration. 
     Air is drawn into the intake manifold  14  by the inlet vacuum created by the engine intake stroke. Air is drawn into the individual cylinders  20  from the intake manifold  14  and is compressed therein. Fuel is injected by the injection system  16  and is mixed with air. The air/fuel mixture is compressed and the heat of compression and/or electrical energy ignites the air/fuel mixture. Exhaust gas is exhausted from the cylinders  20  through exhaust conduits  26 . The exhaust gas drives the turbocharger  18 , which delivers additional air into the cylinders  20  for combustion. 
     The turbocharger  18  is preferably a variable nozzle turbocharger (VNT). The turbocharger  18  includes a plurality of variable position vanes  19  that regulate the amount of air delivered. More specifically, the vanes are movable between a fully-open position and a fully-closed position. When the vanes are in the fully-closed position, the turbocharger  18  delivers a maximum amount of air into the engine  12 . When the vanes are in the fully-open position, the turbocharger  18  delivers a minimum amount of air into the engine  12 . The amount of delivered air is regulated by selectively positioning the vanes between the fully-open and fully-closed positions. The turbocharger  18  includes a vane solenoid  28  that manipulates a flow of hydraulic fluid to a vane actuator (not shown). The vane actuator adjusts the position of the vanes. A vane position sensor  30  generates a vane position signal based on the physical position of the vanes. 
     A control module  32  controls overall operation of the engine system  10 . More specifically, the control module  32  controls engine system operation based on various parameters including, but not limited to, driver input, stability control and the like. The control module  32  can be provided as an Engine Control Module (ECM). The control module  32  regulates operation of the turbocharger  18  by regulating current to the vane solenoid  28 . The control module  32  determines a vane solenoid temperature estimate (T EST ) based on the solenoid temperature estimator of the present invention. The control module  32  performs VNT diagnostics and initiates remedial action based on T EST , as discussed in further detail below. 
     Referring now to  FIG. 2 , the solenoid temperature estimator is created off-line in a laboratory setting using a temperature estimator system  42 . More particularly, a lab-based solenoid driver  44  is provided and includes a pulse-width modulated (PWM) driver module  46 , a high side driver module  48 , a low side driver module  50  and a current module  52 . A voltage supply  54  supplies a voltage (V SUPPLY ) to the lab-based solenoid driver  44 , which generates a PWM current signal to a lab-based vane solenoid  28 ′. A temperature estimator module  55  generates the solenoid temperature estimate based on multi-parameter data point arrays from a data acquisition module  57 . The vane solenoid  28 ′ is disposed within a temperature controlled thermal chamber  56 . The PWM driver module  46  generates a PWM signal based on a commanded duty cycle. The high side driver  48  preferably includes a switching transistor that generates the PWM current signal based on V SUPPLY  and the PWM duty cycle. 
     The low side driver module  50  includes a shunt resistor, through which the current from the vane solenoid  28 ′ flows. The current module  52  measures a voltage drop across the shunt resistor and determines the solenoid current (I SOL ) based thereon. More specifically, the current module  52  includes an amplifier to scale the read voltage drop across the shunt resistor and I SOL  is determined based on the scaled voltage drop. 
     An ambient temperature (T AMB ) within the thermal chamber  56  can be regulated to heat or cool the vane solenoid  28 ′ to mimic ambient temperature conditions that the vane solenoid  28  may experience within the engine system  10 . A temperature sensor  58  is positioned within the thermal chamber  56  in proximity to the coil windings (not shown) inside the vane solenoid  28 ′ and generates a temperature signal indicating a solenoid temperature (T SOL ). The data acquisition module  57  receives data signals from the voltage supply  54 , the lab-based driver  44  and the temperature sensor  58 . More particularly, the data acquisition module  57  receives a voltage signal from the voltage supply  54  and the temperature signal from the temperature sensor  58 . The data acquisition module  57  also receives the commanded PWM duty cycle signal from the PWM driver module  46  and I SOL  from the current module  52 . 
     The solenoid temperature estimator is created based on multiple data entries collected by the data acquisition module  57 . More particularly, each data point is a multi-parameter array including I SOL , T SOL , V SUPPLY  and the PWM duty cycle signal value (X PWM ). Multiple data points are generated for various scenarios. T AMB , V SUPPLY , I SOL  and X PWM  are set and a first data point is determined after each of the signals and T SOL  achieve steady-state. Steady-state is defined as a minimum variance over a threshold period of time. Once steady-state is achieved, the data point is recorded by the data acquisition module  57  as a multi-parameter array and T AMB , V SUPPLY , I SOL  and X PWM  are reset to achieve another steady-state reading. This process is repeated to provide a plurality of steady-state data points that represent the various operating conditions the vane solenoid  28  may experience. The data acquisition module  57  outputs the multi-parameter arrays to the temperature estimator module  55 . The temperature estimator module  55  generates the solenoid temperature estimator. 
     The solenoid temperature estimator can be provided as a look-up table. In the case of a look-up table, the temperature estimator module  55  generates the look-up table based on the data points provided by the data acquisition module  57 . More specifically, a multi-dimensional look-up table is generated based on the multi-parameter arrays of the data points. In this manner, the look-up table provides T EST  based on V SUPPLY , I SOL  and X PWM . In other words, T EST  is equal to T SOL  that was indicated for the particular V SUPPLY , I SOL  and X PWM . 
     Alternatively, the solenoid temperature estimator can be provided as an equation characterized as:
 
 T   EST   =f ( V   SUPPLY   , I   ISOL   , X   PWM )
 
The equation can be derived using a polynomial data fitting technique including, but not limited to, the objective least squares method. In this manner, T EST  is calculated for a given V SUPPLY , I SOL  and X PWM .
 
     Although the temperature estimator system  42  is generally described in terms of physical components, it is anticipated that the temperature estimator system  42  can be a virtual system. More specifically, the temperature estimator system  42  can be programmed as a computer-based simulator. In such a case, the components of the temperature estimator system  42 , including the vane solenoid  28 ′, are software-based models. The virtual temperature estimator system creates the solenoid temperature estimator based on input data (i.e., T SOL , V SUPPLY , I SOL  and X PWM ) and the models process the input data. 
     Referring now to  FIG. 3 , the temperature estimator creation process will be described in further detail. In step  100 , n is set equal to 1. In step  102 , T AMB , the duty cycle and V SUPPLY  are set based on a desired data point (DP n ). DP n  is a single data point in a set of data points (n=1 . . . k) that represent the operating conditions that the vane solenoid may experience. It is determined whether the operating characteristics (e.g., T AMB , duty cycle, V SUPPLY , I SOL  and T SOL ) are at steady-state (i.e., relatively constant for a threshold time) in step  104 . If the operating characteristics are not at steady-state, step  104  is repeated until the operating characteristics achieve steady-state. If the operating characteristics are at steady-state, T SOL , I SOL , V SUPPLY  and PWM duty cycle are read in step  106 . 
     In step  108 , it is determined whether n is equal to k (k=the last data point in the set of data points). If k is not equal to n, n is set equal to n+1 in step  110  and the process is repeated from step  102 . If n is equal to k, the solenoid temperature estimator is generated in step  112  and the process ends. 
     Referring now to  FIG. 4 , an in-vehicle solenoid temperature estimator system  60  includes a control module  62 , a voltage supply  64 , a solenoid driver  66 , a voltage signal filter  68 , a duty cycle signal filter  70 , a current signal filter  72  and a solenoid temperature estimator module  74 . The solenoid driver  66  includes a voltage reading module  76 , a pulse-width modulation (PWM) driver module  78 , a high side driver module  80 , a low side driver module  82  and a current module  84 . The voltage supply  64  supplies a voltage (V SUPPLY ) to the solenoid driver  66 , which generates a PWM current signal to the vane solenoid  28 . The PWM driver module  78  converts the commanded PWM duty cycle signal from the control module  62  to a PWM pulse-train that is used to modulate the high side driver module  80 . The high side driver  80  preferably includes a switching transistor that generates the PWM current signal based on V SUPPLY  and the PWM pulse-train from the PWM driver module  78 . The low side driver module  82  includes a shunt resistor, through which the current from the vane solenoid  28  flows. The current reading module  84  measures a voltage drop across the shunt resistor and determines I SOL  based thereon. More specifically, the current reading module  84  includes an amplifier to scale the read voltage drop across the shunt resistor and I SOL  is determined based on the scaled voltage drop. 
     The voltage signal filter  68  receives a voltage signal indicating V SUPPLY  from the voltage reading module  76 . The duty cycle signal filter  70  receives a duty cycle signal indicative of the commanded PWM duty cycle from the control module  62 . The current signal filter  72  receives a current signal indicative of I SOL  from the current reading module  84 . The filters are preferably digital signal processing (DSP) filters that provide resultant signals having a similar dynamic response to a step change for a given input (e.g., the voltage signal, the duty cycle signal and the current signal). For example, if the commanded duty cycle steps from 50% to 60%, I SOL  may ramp from 1.0A to 1.2A. The filters are designed to cause the resultant signals from the filters to ramp up at the same rate (i.e., duty cycle ramps from 50% to 60% in Y seconds and I SOL  ramps from 1.0A to 1.2A in Y seconds). 
     Although the filter design details are outside of the scope of the present invention, it is anticipated that the filters are application specific and are based on models and/or dynamic test data to account for dynamic electrical and/or software responses of the various modules and the dynamic electrical response from the vane solenoid  28 . It is also anticipated that the filters are designed to include resultant signals based on initial conditions. For example, the filters can generate resultant signals that would provide a default temperature (e.g., a coolant temperature) from the solenoid temperature estimator module  74 . This would occur for a threshold period (e.g., 1 second) after start-up. After the threshold period, the filters provide resultant signals based on the signals provided to each filter. In this manner, erroneous temperature estimates at start-up can be avoided. 
     Referring now to  FIG. 5 , a vehicle control method based on T EST  will be described in detail. In step  200 , V SUPPLY , the duty cycle and I SOL  are determined. V SUPPLY , the duty cycle and I SOL  are filtered in step  202 . In step  204 , T EST  is determined based on the filtered V SUPPLY , duty cycle and I SOL . More specifically, the filtered VsuppLy, duty cycle and I SOL  can be used to reference a multi-dimensional look-up table to determine T EST , as described in detail above. Alternatively, the filtered V SUPPLY , duty cycle and I SOL  can be processed through an equation to determine T EST , as described in detail above. 
     In step  206 , a function is performed based on T EST  and the control method ends. The function can include, but is not limited to, diagnostics, overheat protection, control adjustment and/or further temperature prediction. More specifically, diagnostics that account for vane solenoid temperature can be executed to monitor proper operation of the turbo  18  and/or engine  12 . Additionally, turbo operation or current to the vane solenoid  28  can be limited to prevent overheating of the turbo  18  and/or the vane solenoid  28 . Further, other temperatures can be estimated using T EST . For example, a temperature of the turbo  18  as a whole can be determined using T EST . 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.

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