Patent Publication Number: US-2015068442-A1

Title: Instrument panel with pointer position detection

Description:
TECHNICAL FIELD OF INVENTION 
     This disclosure generally relates to an instrument panel assembly with indicia configured to emit light, and more particularly relates a light detector configured to detect light in the shaft of a pointer that conducts light emitted by the indicia from a tip of the pointer into the shaft when the tip is substantially aligned with the indicia. 
     BACKGROUND OF INVENTION 
     When vehicle instrument panel assemblies with traditional pointers are manufactured, a camera is used to determine any offset error between the actual pointer location and a desired pointer location corresponding to an indicia or grad on the display. This offset is programmed into the instrument panel to ensure that the offset is applied each time the instrument panel is powered. If power to the instrument panel is interrupted during normal operation, the instrument cluster does a “homing” operation to spin the pointer back to a zero position. As the pointer angle is unknown when power is applied, occasionally the motor will hit an internal hard-stop with enough force that motor drive bounces back out a step or two, and so the gauge becomes inaccurate. 
     SUMMARY OF THE INVENTION 
     In accordance with one embodiment, a vehicle instrument panel assembly is provided. The assembly includes a display, a pointer, and a light detector. The display is configured to define indicia on a surface of the display. The indicia are configured to emit light. The pointer is configured to rotate a shaft of the pointer about an axis to align a tip of the pointer with the indicia. The pointer is also configured to conduct light emitted by the indicia from the tip into the shaft when the tip is substantially aligned with the indicia. The light detector is configured to detect light in the shaft of the pointer to determine the position of the pointer. 
     Further features and advantages will appear more clearly on a reading of the following detailed description of the preferred embodiment, which is given by way of non-limiting example only and with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The present invention will now be described, by way of example with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a vehicle interior equipped with an instrument panel assembly in accordance with one embodiment; 
         FIG. 2  is an exploded perspective view of the instrument panel of  FIG. 1  in accordance with one embodiment; and 
         FIG. 3  is a sectional side view of the portion of a vehicle instrument panel assembly of  FIG. 1  in accordance with one embodiment; and 
         FIG. 4  is a close-up sectional view of a portion of the instrument panel of  FIG. 1  in accordance with one embodiment. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a non-limiting example of a vehicle  10  equipped with an instrument panel assembly, hereafter referred to as the assembly  12 , installed into a dashboard  16  of the vehicle  10 . In general, the assembly  12  displays vehicle information to a human  14  or operator of the vehicle  10  such as vehicle speed, engine coolant temperature, and the like. 
       FIG. 2  illustrates a non-limiting example of the assembly  12  as it might appear when not installed into the dashboard  16  of the vehicle  10 . In general, the assembly  12  includes an applique  18 . In this example the applique  18  spans most of the viewing area of the assembly  12 . The assembly  12  also typically includes a lens  22  for protecting the pointers  24  and the applique  18  from contact damage and contaminants. The applique  18  typically includes graphics and indicia  26  that help to determine the appearance of an instrument panel (the assembly  12 ). Some of the indicia  26  are configured to become visibly apparent to the human  14  only when suitably backlit. As will become apparent in the description that follows, of particular interest are the radially oriented indicia that are sometimes referred to as tick marks. 
     As such, the assembly  12  or display  30  is configured to define indicia  26  on a surface of the display  30 , and the indicia  26  are configured to emit light. Backlighting of the applique  18  is generally provided by a number of light sources, for example a display light source  28  ( FIG. 3 ). These light sources are preferably light emitting diodes (LEDs), as LEDs are reliable, economical, and typically generate less heat than other types of light sources such as incandescent bulbs. However, the assembly  12  described herein is not limited to using LEDs as light sources. The applique  18  overlays the display light source  28 . The applique  18  also defines a transmissive portion  32  of the applique  18  that corresponds to the indicia  26 . 
     Referring now to  FIG. 3 , the assembly  12  also includes a pointer  24  configured to rotate a shaft  34  of the pointer about an axis  36  to align a tip  46  of the pointer  24  with the indicia  26 . Light  48  is emitted via the transmissive portion  32  of the applique  18  that forms the tick marks, i.e. the indicia  26 . As the pointer  24  sweeps across the surface of the display  30 , the tip  46  passes over these tick marks the light  48  propagates down the pointer toward the shaft  34 . Accordingly, the pointer  24  is generally made of material transmissive of light, clear polymeric compound for example. As such, the pointer is configured to conduct light  48  emitted by the indicia  26  from the tip  46  into the shaft  34  when the tip  46  is substantially aligned with the indicia  26 . As used herein, ‘substantially aligned’ means that the pointer  24  is aligned with the indicia  26  with enough precision that the position of the pointer  24  can be known accurately enough to determine if there is an error between the desired position and the actual position of the pointer to warrant adjusting or recalibrating the aspects of the assembly  12  that control the position of the pointer  24 . By way of example and not limitation, the tip  46  may be substantially aligned when the pointer is within one degree (+/−1°) of angle. 
     In order to detect the light  48  in the shaft  34 , the assembly is equipped with a light detector  40 . In general, the light detector  40  is configured to detect the light  48  in the shaft  34  of the pointer  24  to determine the position of the pointer  24 . In this non-limiting example, the light detector  40  is shown in line with the axis. Alternatively, the light detector  40  may be offset from the axis if the pointer  24  is supported by a bearing that is centered on the axis  36 . 
     The assembly  12  may include a controller  38  in electrical communication with the display light source  28  and the light detector  40 . The controller  38  may include a processor such as a microprocessor or other control circuitry as should be evident to those in the art. The controller  38  may include memory, including non-volatile memory, such as electrically erasable programmable read-only memory (EEPROM) for storing one or more routines, thresholds and captured data. The one or more routines may be executed by the processor to perform steps for determining if signals received by the controller  38  from the light detector  40  indicate that the pointer  24  is aligned with the indicia  26 . Optionally, the controller  38  is configured to output a modulation signal to the display light source  28 , and is configured to receive a detection signal from the light detector  40  effective for the controller  38  to determine if the tip  46  is aligned with the indicia  26  whereby the light  48  from display light source  28  is detected by the light detector  40 . 
     The light detector  40  may be attached to a circuit board  50  and the pointer  24  may be rotated by a stepper motor  52  that may also be controlled by the controller  38  (connection not shown), as will be recognized by those in the art. 
     The pointer  24 , in particular the tip  46 , may include a reflective element  44  configured to reflect the light  48  from the indicia  26  toward the shaft  34 . The reflective element  44  may be formed by adding a reflective coating to the appropriate surfaces of the pointer  24 , or may be a small mirror formed of glass or polished metal that is insert-molded into the pointer  24  near the tip  46 , as will be recognized by those in the art. 
       FIG. 4  illustrates a non-limiting example of a portion of the assembly  12 . In addition to the light detector  40 , the assembly  12  may include a pointer light source  42  configured to emit light into the shaft for illuminating the pointer  24 . It has been observed that the light detector  40  is able to distinguish the light  48 A originating from the display light source  28  from the light  48 B originating from the pointer light source  42 . However it is recognized that certain ambient lighting conditions may make such detection difficult. As such, the pointer light source  42  and/or the display light source  28  may be modulated (e.g. pulse-width-modulated) in such a manner that the controller  38  is able to distinguish the light  48 A originating from the display light source  28  from the light  48 B originating from the pointer light source  42 , and thereby determine if the tip  46  is aligned with the indicia  26 . 
     Accordingly, a vehicle instrument panel assembly (the assembly  12 ) is provided. The pointer  24  is configured so light emitted by the display light source  28  through the indicia  26  propagates through the pointer to the light detector. The controller  38  receives a signal from the light detector  40  indicative of the amount of light detected by the light detector  40 , and determines if the tip  46  is substantially aligned with the indicia based on the signal from the light detector  40 . In this way, the controller  38  is able to determine if the actual position of the pointer  24  corresponds with the desired position of the pointer which is controlled by the controller  38  by way of, for example, a stepper motor  52 . In an alternative configuration, the indicia  26  or tick marks may be features of a trim ring configured to emit light at certain locations that can be used to determine if the pointer  24  is properly aligned. 
     While this invention has been described in terms of the preferred embodiments thereof, it is not intended to be so limited, but rather only to the extent set forth in the claims that follow.