Abstract:
A hydraulic solenoid assembly for complex vehicle-borne control systems, such as automatic transmissions, includes a solenoid body or unitary housing operatively enclosing two or more solenoid valves. Each valve has a pressure port extending to an outer surface of the housing, emerging in a spaced-apart matrix. A metal (stainless steel or aluminum) sensor plate is mounted to the outer surface of the housing so as to sealingly overlay the pressure ports. A diaphragm is formed in the sensor plate for each solenoid valve and registers with its associated pressure port. Electrical components, such as thick file resistors arranged in a Wheatstone bridge network are printed or mounted to an outer surface of each diaphragm. The bridge networks are electrically connected to a control circuit and function to output signals as a function of hydraulic pressure induced displacement of the associated diaphragm.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a national stage application under 35 U.S.C. 371 of PCT Application No. PCT/US2011/038982 having an international filing date of 3 Jun. 2011, which designated the United States, which PCT application claimed the benefit of U.S. provisional patent application Ser. No. 61/351,376 filed 4 Jun. 2010, entitled “Multiple Hydraulic Circuit Pressure Sensor”, the entire disclosure of each of which are hereby incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to hydraulic solenoid valves, and particularly to the control of complex hydraulic systems employing multiple solenoid valves using direct hydraulic circuit pressure sensing techniques. 
       BACKGROUND OF THE INVENTION 
       [0003]    Known transmission control technology utilizes solenoid “current” sensing to close the control loop within the transmission requiring extremely high precision, costly transmission components to achieve the desired functionality. 
         [0004]    Known pressure sensing technology typically consists of individually packaged, self-contained pressure sensors for each hydraulic solenoid circuit. Automotive transmission applications typically require 6-8 sensors, depending on the number of gear ratios employed. Other complex automotive applications, such as anti-lock braking systems (ABS), traction control systems (TCS), active stability control systems (ASCS), and the like often require a similar number of sensors. In addition to being expensive, known sensors are large and can be difficult to package in a confined automotive environment. As a result, closed loop pressure control techniques have not been widely applied to automotive applications. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention provides a cost effective, compact/small form factor method to directly sense line pressures of hydraulic control systems within complex automotive hydraulic systems such as automatic transmissions. This is desirable inasmuch as it provides dynamic real time pressure information to the associated controller enabling closed loop pressure control algorithms within the transmission. Closed loop pressure control within the transmission enables easier and more precise transmission closed loop control calibration and can provide better compensation for transmission component wear and fluid contamination over the service life of the transmission. Precise pressure feedback may also enable reduction of transmission parasitic losses through more precise shifting and facilitating “on-demand” transmission fluid pump management, resulting in better vehicle fuel economy and lower CO2 emissions. 
         [0006]    These and other features and advantages of this invention will become apparent upon reading the following specification, which, along with the drawings, describes preferred and alternative embodiments of the invention in detail. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The present invention will now be described, by way of example, with reference to the accompanying drawings, in which: 
           [0008]      FIG. 1 , is an exploded, perspective view of a hydraulic solenoid assembly suitable for installation in a vehicle transmission housing including a unitary solenoid body containing six solenoids juxtaposed for assembly with a sensor plate carrying six pressure sensors; 
           [0009]      FIG. 2 , is a broken, plan view of the underside of a portion of the sensor plate, illustrating a generally circular intermediate pressure sensing diaphragm disposed between two adjacent partial sensing diaphragms; 
           [0010]      FIG. 3 , is a broken, cross-sectional schematic view of a portion of the sensor plate taken along lines  3 - 3  of  FIG. 2 , illustrating the configuration of one of the integrally formed sensing diaphragms; 
           [0011]      FIG. 4 , is a broken, plan view of the underside of a portion of a first alternative embodiment of the sensor plate, illustrating (in solid line) a pressure sensing diaphragm which is elongated along the longitudinal (X) axis, and (in phantom) a pressure sensing diaphragm which is elongated in the lateral (Y) axis; 
           [0012]      FIG. 5 , is a broken, cross-sectional schematic view of a portion of a second alternative embodiment of the sensor plate taken, illustrating the configuration of one of the integrally formed sensing diaphragms; 
           [0013]      FIG. 6 , is a partial cross-sectional, perspective view of the assembled solenoid body with pressure port, the metal sensor plate forming a sensor overlaying the pressure port, and a protective cover overlaying the sensor plate; 
           [0014]      FIG. 7 , is a cross-sectional view of a portion of the sensor plate defining a sensor diaphragm cavity and associated printed resistors in the relaxed position on an enlarged scale; 
           [0015]      FIG. 8 , is a cross-sectional view of the sensor of  FIG. 12  in a pressurized condition wherein the sensor diaphragm is deflected, thereby subjecting the associated printed resistors to tension or compression; and 
           [0016]      FIG. 9 , is a schematic of a six pressure cell circuit. 
       
    
    
       [0017]    Although the drawings represent embodiments of the present invention, the drawings are not necessarily to scale and certain features may be exaggerated in order to illustrate and explain the present invention. The exemplification set forth herein illustrates an embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0018]    The present invention describes a multiple hydraulic circuit pressure sensor for automotive transmission applications. The sensor utilizes thick film electronics printing techniques on a stainless steel or aluminum plate to create a unified structure with multiple sensor locations that can be mounted over multiple solenoid pressure port locations inside the transmission. The plate contains Wheatstone bridge thick film printed resistor configurations over shaped diaphragm locations to measure diaphragm deformation due to applied pressure. In addition, the plate forms its own “circuit board” containing all of the circuit routing and reflow solder electrical components necessary to create a self-contained, functional multiple location sensing circuit. The plate construction is impervious to immersion in hot transmission fluid. 
         [0019]    The sensing plate allows several independent sensing locations to be produced in one pass through the manufacturing value stream (e.g. multiple sensing locations are printed all at once, component placement and solder for multiple sensing locations in one pass through SMT, etc.). This results in significantly less manufacturing cost that of processing and packaging each sensor discretely. Early estimates show a significant cost savings over conventional individual in transmission sensor architecture. 
         [0020]    Representative thick film pressure sensor technology applicable to the present invention is described in U.S. Pat. No. 5,867,886 to Ratell et al. entitled “Method of Making a Thick Film Pressure Sensor” and in U.S. Pat. No. 5,898,359 to Ellis entitled “Diffusion-Barrier Materials for Thick-Film Piezoresistors and Sensors Formed Therewith”. A representative solenoid valve applicable to the present invention is described in U.S. Pat. No. 6,901,959 B2 to Burrola et al. entitled “Three Port Solenoid Valve”. U.S. Pat. Nos. 5,898,359, 5,867,886 and 6,901,959 are hereby incorporated herein in their entirety by reference. 
         [0021]    The preferred embodiment of the present invention is unique inasmuch as it has a very small form factor for ease of packaging inside the host vehicle transmission, its low cost potential, and its durability within the transmission fluid and temperature environment. 
         [0022]    Referring to  FIG. 1 , a multiple hydraulic circuit device  10  includes a solenoid body assembly  12  and a sensor assembly  14 . Although having many possible applications, the device  10  is particularly advantageously applied for hydraulic control solenoids located inside an automotive transmission, submerged in automatic transmission fluid. The solenoid body assembly  12  houses a plurality (six are illustrated) of solenoid valves  16   a - 16   f , each having an associated pressure port  18   a - 18   f  opening through a common planer upper surface  20 . The pressure ports  18   a - 18   f  are equally spaced and aligned along a longitudinal axis (X) of elongation. The solenoid valves  16   a - 16   f  emerge from a side wall  22  of body assembly  12 . 
         [0023]    The sensor assembly  14  is built on a single stainless steel or aluminum plate  24  which is elongated along axis X. The plate  24  has an upper surface  26  having six resistor bridge circuits  28   a - 28   f , a multi-circuit connector  30  and interconnecting conductive traces  32  formed thereon. The connector  30  is configured for electrically interfacing the device  10  with the power supply and control circuitry (not illustrated) of an associated host vehicle. The plate  24  has a lower surface  34  which overlays the upper surface  20  of the solenoid body assembly  20  to sealingly close the pressure ports  18   a - 18   f  at their point of emergence through upper surface  20 . 
         [0024]    Referring to  FIGS. 2 and 3 , a broken, representative portion of the sensor assembly  14  illustrates details thereof on an enlarged scale. A blind bore or recess  36   a - 36   f  associated with each resistor bridge circuit  28   a - 28   f  opens downwardly through the lower surface  34  of the sensor plate  24  in register with an associated underlying pressure port  18   a - 18   f . Each recess  36   a - 36   f  is closed adjacent the upper surface  26  of the sensor plate  24  by an associated diaphragm  38   a - 38   f  integrally formed with the material forming the balance of the sensor plate  24 . 
         [0025]    In application, pressurized hydraulic fluid within pressure ports  18   a - 18   f  is applied against the lower surface  40   a - 40   f  of each associated diaphragm  38   a - 38   f , locally distending the diaphragm  38   a - 38   f  upwardly as a function of hydraulic fluid pressure as indicated by arrow  42 . 
         [0026]    Nominally, each diaphragm has a thickness “T”, and the supportive adjacent portion of the sensor plate  24  has a thickness of “3T”. Furthermore, each blind bore  36   a - 36   f  has a nominal diameter “D” and is spaced from adjacent blind bores at least by dimension “D”. Such dimensional relationships provide a robust design wherein the diaphragms can locally flex while the supportive portions of the sensor plate remain rigid, preventing leakage of hydraulic fluid and “cross-talk” between adjacent diaphragms  38   a - 38   f.    
         [0027]    The dimensions and shape of the diaphragms  38   a - 38   f  can be altered as required for a given application. The embodiment illustrated in  FIGS. 1-3  depict round diaphragms  38   a - 38   f , each having a thickened center portion  44   a - 44   f  and a concentric outer portion  46   a - 46   f.    
         [0028]    Referring to  FIG. 4 , a sensor assembly  48  includes a sensor plate  50  defining an oval shaped blind bore  52  elongated, by way of example, along the X axis or, alternatively, (in phantom) along the Y axis as  52 ′. As viewed from a bottom perspective, blind bore  52  is closed by a similarly elongated diaphragm  54 . 
         [0029]    Referring to  FIG. 5 , another alternative embodiment of the present invention illustrates a sensor assembly  56  having a sensor plate  58  forming a blind bore  60  closed by a diaphragm  62  having a relatively thin center portion  64 , a radially tapered intermediate portion  66  and locally thinned outermost portion  68 . The shape of the diaphragm can be altered to tailor displacement thereof when transitioning between a relaxed (unpressurized) position and a distended (pressurized) position as referenced by arrow  70 . 
         [0030]    Referring to  FIGS. 6-8 , yet another embodiment of the present invention is illustrated. A multiple hydraulic circuit device  72  includes a solenoid body or housing  74  (solenoids are not illustrated for the sake of simplicity) with a sensor assembly  76  mounted thereon. The solenoid body  74  forms passageways  78 ,  80  and  82  for receiving solenoid mechanisms therein and routing hydraulic fluid. Passageway  80  hydraulically communicates with the upper surface  84  of solenoid body  74  through a pressure port  86 . The sensor assembly  76  includes a sensor plate  88  forming a blind bore  90  therein registering with the pressure port  86 . The blind bore  90  is closed by a diaphragm  92  located adjacent the upper surface  94  of the pressure plate  88 . The diaphragm  92  is relatively thin and is locally displaceable under the influence of pressurized hydraulic fluid as indicated by arrow  96 . 
         [0031]    A protective member  108  overlays the upper surface  94  of the sensor plate  88  and is secured in assembly with the solenoid body  74  by through-fasteners (not illustrated) compressively securing the sensor plate  88  in its illustrated position. The protective member  108  prevents displacement of the sensor plate  88 , and thus, cross-talk between adjacent resistor bridge circuits  98 . The protective member  108  has a relief feature  110  formed therein located concentrically with an underlying diaphragm  92 . The relief feature  110  forms a cavity  112  and includes a top portion  114  spaced above the diaphragm  92 , enabling clearance along the Z axis for momentary displacement of the diaphragm  93  as depicted in  FIG. 8 . 
         [0032]    A resistor bridge network  98  is printed on the outer surface  94  of the diaphragm  92 . The resistor bridge network  98  has a first set (one or more) of resistors  100  located in a central region  102  of the diaphragm  92  which are subjected to substantially tensile loading when the underlying diaphragm  92  is displaced from an unloaded or rest position (as illustrated in  FIG. 7 ) to a deflected or loaded position (as illustrated in  FIG. 8 ), and a second set (one or more) of resistors  104  located in an outer region  106  of the diaphragm  92  which are subjected to substantially compressive loading when the underlying diaphragm  92  is displaced from an unloaded or rest position (as illustrated in  FIG. 7 ) to a deflected or loaded position (as illustrated in  FIG. 8 ). 
         [0033]    The first set of resistors  100 , being located in the central region  102  are stretched or subjected to tensile loading as a result of the diaphragm  92  being deformed from the position illustrated in  FIG. 7  to the position illustrated in  FIG. 8 . Conversely, the second set of resistors  104  are compressed or subjected to compressive loading as a result of the diaphragm  92  being deformed from the position illustrated in  FIG. 7  to the position illustrated in  FIG. 8 . Preferably, a portion of each of the second set of resistors  104  is effectively fixedly grounded to a relatively non-displaceable, relatively thick portion of the pressure plate  88  and an opposed portion of each of the second set of resistors  104  is effectively carried for displacement with the outer region  106  of the diaphragm  92  being deformed from the position illustrated in  FIG. 7  to the position illustrated in  FIG. 8 . 
         [0034]    Referring to  FIG. 9 , an electrical block diagram  116  depicting a six cell sensor circuit is illustrated. A plurality of cells  118   a - 118   f  are each in-circuit with a compensator array  120  along with a suitable power supply and an electrical ground. Each cell  118   a - 118   f  is associated with a single diaphragm and the first and second sets of printed resistors collectively forming a Wheatstone bridge. The compensator array  120  provides output signals on output lines  122   a - 122   f , each corresponding with one of the cells  118   a - 118   f.    
         [0035]    It is to be understood that the invention has been described with reference to specific embodiments and variations to provide the features and advantages previously described and that the embodiments are susceptible of modification as will be apparent to those skilled in the art. 
         [0036]    Furthermore, it is contemplated that many alternative, common inexpensive materials can be employed to construct the basis constituent components. Accordingly, the forgoing is not to be construed in a limiting sense. 
         [0037]    The invention has been described in an illustrative manner, and it is to be understood that the terminology, which has been used is intended to be in the nature of words of description rather than of limitation. 
         [0038]    Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, wherein reference numerals are merely for illustrative purposes and convenience and are not in any way limiting, the invention, which is defined by the following claims as interpreted according to the principles of patent law, including the Doctrine of Equivalents, may be practiced otherwise than is specifically described.