Abstract:
A control methodology for a wireless oil level sensor includes mounting a wireless oil pressure sensor to the oil plug of an engine. The oil pressure sensor detects a pressure which is used to determine a volume or level of oil in the oil pan. The oil level sensor can include an accelerometer sensor that can be excited by the vibration caused by the starting of the engine to “wake up” the sensor. The sensor can take an initial pressure reading at start up and associate the pressure reading with an oil level that can then be transmitted to a vehicle control unit. The sensor can remain idle until the accelerometer sensor no longer detects engine vibrations. The sensor is activated to take pressure readings at predetermined time intervals and to transmit an associated oil level to the vehicle central processor unit until a predetermined time period has expired.

Description:
FIELD 
     The present disclosure relates to a control methodology for a wireless fluid level sensor and more particularly to a wireless oil level sensor for an internal combustion engine. 
     BACKGROUND AND SUMMARY 
     This section provides background information related to the present disclosure which is not necessarily prior art. 
     It is important to maintain a proper amount of oil in an engine in order for the engine to be properly lubricated. Typically, engines are equipped with a dipstick that is manually removed from an engine in order to observe the oil level of the oil on the dipstick. Although the oil dipstick is a reliable method of detecting the oil level, it requires that the vehicle operator open the vehicle hood and pull the dipstick out of the engine. Optional engine oil switches exist that notify an operator that the oil level is low. These oil switches have to be wired into the vehicle and fixedly mounted within the oil pan at a level representative of a minimum level at which the user needs to be notified of the low oil condition. Therefore, the typical oil level sensor is only useful for providing a low oil indicator when a low oil condition exists. 
     The present disclosure provides implementation and a control methodology of a wireless oil level sensor. The control methodology includes mounting a wireless oil pressure sensor to the oil plug of an engine. The oil pressure sensor detects a pressure which can then be used to determine a volume or level of oil above the sensor. The oil level sensor can include an accelerometer sensor that can be excited by the vibration caused by the starting of the engine to “wake up” the sensor. The sensor can take an initial pressure reading at start up and associate the pressure reading with an oil level that can then be transmitted to a vehicle control unit. The sensor can remain idle until the accelerometer sensor no longer detects engine vibrations at which time the sensor is activated to take pressure readings at predetermined time intervals and to transmit an associated oil level to the vehicle central processor until a predetermined time period has expired. The oil sensor then goes into sleep mode in order to maximize battery life. 
     According to another aspect of the present disclosure, the oil sensor can further be utilized to detect an oil change condition and report the oil change condition to the vehicle control unit so that the oil life monitor can be automatically reset without requiring any input from the vehicle operator. 
     According to a further aspect of the present disclosure, the oil sensor can be utilized to estimate crankcase pressure during engine operation to help service technicians determine if the crankcase ventilation system or piston rings are operating properly. 
     Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure. 
         FIG. 1  is a schematic view of a vehicle having an engine with a wireless oil sensor disposed in the oil pan according to the principles of the present disclosure; 
         FIG. 2  is a schematic view of an engine with the wireless oil sensor disposed in the oil pan according to the principles of the present disclosure; 
         FIG. 3  is a schematic view of the oil sensor mounted to the oil plug received in the oil pan; and 
         FIG. 4  is a schematic diagram illustrating the communication between the wireless oil sensor and a vehicle control unit according to the principles of the present disclosure. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     Example embodiments will now be described more fully with reference to the accompanying drawings. 
     Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. 
     The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     With reference to  FIG. 1 , a vehicle  10  is shown including an engine  12  having an oil pan  14  with an oil sensor  16  disposed in the oil pan. The oil sensor  16  can provide wireless signals to the vehicle central processor unit  18  which can display information to the vehicle operator via a vehicle display unit  20 .  FIG. 2  shows a larger more detailed view of the engine  12  oil pan  14  with the oil sensor  16  disposed in the oil pan plug  22 .  FIG. 3  shows a larger more detailed view of the oil pan plug  22  disposed in a threaded opening  24  in the bottom of the oil pan  14  and with the oil sensor  16  mounted to the oil pan plug  22 . 
       FIG. 4  provides a schematic illustration of the components of the wireless oil sensor  16  for communication with the vehicle central processor unit  18 . The wireless oil sensor  16  includes a sensor central processor unit  30  that is in communication with a plurality of sensors that can include a pressure sensor  32 , temperature sensor  34 , an accelerometer sensor  36 , and an attitude sensor  37 . Additional sensors can be utilized. A battery  38  is provided for providing power to the wireless oil sensor  16  and an RF transceiver  40  is provided for providing signals to and transmitting signals from the central processor unit  30 . The RF transceiver  40  is capable of transmitting signals to an RF transceiver  42  of the vehicle central processor unit  18  as well as receiving signals from the RF transceiver  42  or from other programming tools  50  ( FIG. 1 ). 
     The sensor function begins with the sensor in a sleep mode when the engine is off. When the “Key” is turned “on” or the engine is otherwise caused to turn over, the accelerometer sensor  36  is excited by the vibration of the engine and it causes the oil sensor  16  to switch to an operation/awake mode. The oil sensor  16  then immediately reads the temperature and pressure within the oil pan  14  and can convert those temperature and pressure readings into a corresponding oil level (L) at start-up. It is noted that for purposes of the discussion herein, the oil level L and sensed pressure P are used somewhat interchangeably since the sensed pressure generally corresponds to a certain oil level. Optionally, oil level can be converted to oil mass by assuming a known oil density and correcting for temperature. The sensor readings are required to be taken right away before engine operation causes the oil to be dispersed throughout the lubrication system of the engine so that the level of oil in the oil pan  14  is not representative of the amount of oil that is typically measured when the engine is off. The sensor readings are also required before the oil crankcase atmospheric pressure is affected by the engine operation. During the remaining engine operation cycle, the oil sensor  16  can remain idle. 
     When the key is turned “off” or the engine is otherwise turned off, the excitation of the accelerometer sensor  36  is stopped. After the oil sensor  16  detects that the engine vibration has stopped via the accelerometer sensor  36 , the oil sensor central processor unit  30  initiates a clock and begins sampling the oil level at predetermined increments for a predetermined period of time. By way of non-limiting example, the predetermined increments can be 10 sec increments and the predetermined period of time can be determined based upon a typical amount of time for a majority of the engine oil to return to the oil pan  14 . This time period can range from 1 minute to several minutes for different engine designs. The oil sensor central processor unit  30  can correct the oil level for temperature and optional volume variations or mass and transmit the oil level/volume for each level read to the radio frequency transceiver  42  of the vehicle central processor unit  18 . After the predetermined time period has expired, the oil sensor  16  returns to sleep mode. 
     The control method of the wireless oil sensor  16  enables the wireless sensor  16  to act autonomously in its environment. The wireless oil sensor is capable of sensing its own environment and can be selectively energized to measure the fluid level when it is possible for accurate measurement. The battery life of the oil sensor is maximized due to the selective operation. The control methodology of the present disclosure enables the use of a wireless engine oil level sensor and has the potential to replace the current oil level dipstick and low oil switch used in present vehicles. The system can result in cost reduction, improved oil level measurement accuracy, improved customer convenience by allowing accurate oil level information to be displayed on a vehicle display  20 . The attitude sensor  37  can be utilized to adjust the oil level reading for tilt if the vehicle is parked on a hill. Therefore, a false low oil level indication can be avoided. 
     A further feature of the present disclosure is the ability to use the wireless oil sensor  16  to include an algorithm to recognize the environmental conditions that are unique to an oil change. In general, it is recognized that an oil level changes very slowly throughout the operation of a vehicle whereas an oil change will induce a change in oil level over a very short period of time. The oil sensor  16  is able to recognize an oil change event and communicate to the vehicle central processor unit  18 . In particular, according to one aspect of the present disclosure, the oil sensor  16  can calculate a change in oil level with respect to time (dL/dT) and determine if the value of dL/dT is less than 0 and its absolute value is greater than a threshold value, then an oil change event is identified. In other words, in the event the oil sensor  16  is mounted to the oil plug  22 , removal of the oil plug and oil sensor  16  will result in the oil sensor being activated from sleep mode by the accelerometer being excited due to the rotation and removal of the oil plug  22 . Once the oil plug  22  and oil sensor are removed from the oil pan, the oil sensor  16  will recognize an immediate drop in pressure since the pressure sensor  32  is now exposed to ambient pressure. The drop in pressure can be identified as an oil change event that can be identified to the vehicle central processor unit  18  which can either automatically update the vehicle database of the current oil change event or to prompt the vehicle operator via the display  20  to confirm that an oil change is or has been performed. As an alternative, the attitude sensor  37  can be used to detect that the oil plug was removed to signal that an oil change is being performed. The removal of the oil plug would alter the attitude of the oil plug and allow the vehicle central processor unit to discern that an oil change is being performed. 
     If the oil sensor  16  is not mounted to the oil plug  22 , but is otherwise mounted within the oil pan  14 , the oil sensor  16  will recognize a rapid decrease in pressure over time (dL/dT) as the oil drains from the oil pan  14 . The rapid decrease in pressure over time can be determined to be representative of an oil change event that can be identified to the vehicle central processor unit  18  which can either automatically update the vehicle database of the current oil change event to reset the oil life monitor or to prompt the vehicle operator via the display  20  to confirm that an oil change is or has been performed, and then, if confirmed, can reset the oil life monitor. 
     According to an alternative oil change check function, a repetitive knocking on the surface of the oil plug  22  in close proximity to the oil sensor  16  can be recognized by the accelerometer sensor  36  and the oil sensor  16  can transmit to the vehicle central processor unit  18  signaling an oil change event in progress. The repetitive knocking can be representative of a wrench engaging the oil plug  22  or another forced pattern that the oil change technician carries out. A repeated knocking pattern (either via re-installation of the oil plug  22  or a forced pattern carried out by the oil change technician) can then be recognized by the accelerometer  36  and the oil sensor  16  can transmit information to the vehicle central processor unit  18  to signal that the oil change event is complete so that the oil life monitor can be automatically reset, either with or without confirmation of the oil change event with the vehicle operator. The oil change detection feature provides a means by which the oil life monitor on a vehicle can be automatically reset rather than requiring vehicle operator input. 
     According to a further aspect of the present disclosure, the oil sensor  16  located in the oil pan drain plug  22  can be used to estimate crankcase pressure during various operating conditions of the engine to determine if the ventilation system or piston rings are operating properly. Service technicians currently have to install a separate blow-by measuring device onto the engine to determine if the piston rings are not sealing properly. Service technicians also have no means of measuring the crankcase pressure to determine if the ventilation system is operating correctly. The use of the oil sensor  16  to estimate the pressure during engine operation eliminates the need to install a separate crankcase pressure sensor and/or a blow-by measurement device, which saves labor and diagnosis time. In order to use the oil sensor  16  for detecting engine operating conditions, the technician starts the engine and lets it idle. The technician uses a hand held signal monitoring device  50  ( FIG. 2 ) or vehicle display  FIG. 2  to read a pressure output from the oil sensor  16 . By way of non-limiting example, pressure values lower than a normal predetermined value (e.g. −4 kPa) can indicate that the crankcase pressure regulation valve is stuck in an open position and requires service. Pressure values higher than a normal predetermined value (e.g. 3 kPa) indicate that the piston rings are not sealing properly or the pressure regulation valve is stuck closed. Accordingly, the oil pressure sensor in the oil pan can be used by service technicians to diagnose engine problems. 
     An alternative to the technician activating the sensor using a signal monitoring device, is an “automated mode” that detects crankcase pressure periodically during engine operation and reports to the engine central processor unit  18 . The central processor unit  18  captures the signal and determines if the engine is in the required “standard” condition (e.g., warm idle). If so, the central processor unit  18  checks for pressure values being in the “normal” window. If not, the central processor unit  18  provides a signal to notify the operator of possible maintenance requirements. 
     The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.