Abstract:
A device for determining a load applied to an object for regulating a window or a closure or a partition, the device comprising a printed circuit board and a gauge capable of providing an output from which the load may be derived or inferred, the gauge being formed integrally as part of the printed circuit the device being so constructed and arranged as to be capable of mounting the object to a fixed body.

Description:
[0001]    This application claims priority to United Kingdom (GB) Patent Application Number 0117867.2 filed on Jul. 21, 2002.  
         BACKGROUND OF THE INVENTION  
         [0002]    The present invention relates to a device for determining loads. In particular, the present invention relates to a device for determining torque loads applied to a component such as a vehicle component.  
           [0003]    Vehicles are known whereby doors of such vehicles include windows which can be power opened and power closed. When a window is being power closed, it is possible for parts of people, and in particular children, to get trapped in between the window and window surround. In order for such windows to function within legal and other requirements, it is necessary to avoid applying more than a certain, predetermined maximum force to an arm, finger or other part of the body when that part of the body interferes with the normal closure of the window. Equally, it is necessary to ensure that a sufficient force is available to fully close the window into its seals. To this end, the relevant specifications allow for the limited force to be exceeded once the opening is smaller than would admit entry of any part of the body.  
           [0004]    Thus, in known contact type anti-trap (anti-squeeze) systems a switch, typically within the door seal, is closed when a body part is trapped, and this triggers a decision within a control unit to stop or reverse the closing motion, and thereby release the body part.  
           [0005]    Other known contact type anti-squeeze systems rely on an inference of trap force from a parameter measurable at the motor such as change in motor speeds, change in motor current or change in output torque, all of which are related to the forces applied to the closure i.e. the output force of the actuator assembly.  
           [0006]    The aforesaid systems generally quite complex and require a high part count, which inevitably increases the unit cost of manufacturing and installing such systems.  
           [0007]    One object of the present invention is to provide a lower cost anti-trap system requiring fewer components and a simpler assembly process.  
           [0008]    Furthermore, due to rough roads or other terrain over which the vehicle may be travelling, triaxial accelerations with a significant vertical component are imposed on the vehicle. These vertical accelerations are applied to the window glass as to any other part of the vehicle and are reacted through the window regulator as variations in closure force. Under some circumstances these variations may produce forces on the window glass which resemble the forces produced when body parts are trapped. Under such circumstances the control unit will incorrectly reopen the window when this is unnecessary. Alternatively when a body part is being trapped, accelerations on the window glass due to rough terrain may reduce the apparent trapping force to below the predetermined level whereupon closure will continue and further trap a body part.  
           [0009]    Thus, situations arise which are inconvenient and/or distracting and are potentially dangerous for the occupants of the vehicle.  
           [0010]    A further object of the present invention is to provide an improved form of closure system.  
         SUMMARY OF THE INVENTION  
         [0011]    Accordingly, one aspect of the invention provides a device for determining a load applied to an object for regulating a window or a closure or a partition, the device comprising a printed circuit board and a gauge capable of providing an output from which the load may be derived or inferred, the gauge being formed integrally as part of the printed circuit.  
           [0012]    A second aspect of the present invention provides a closure system including a closure moveable for substantially closing an aperture in use, and an actuator for at least closing the closure, the actuator being mounted by a mount, the mount including one or more gauges for measuring, in use, parameters of the closure systems, in use the closure system being subjected to accelerations and being arranged such that it is possible to at least partially distinguish forces applied to the closure by the actuator from acceleration forces applied to the closure as a result of the accelerations of the closure system. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    The various features and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the currently preferred embodiment. The drawings that accompany the detailed description can be briefly described as follows:  
         [0014]    [0014]FIG. 1A is a schematic side view of a vehicle including a closure system incorporating a device according to the present invention.  
         [0015]    [0015]FIG. 1B is a cutaway view of a door illustrating an alternative closure system incorporating a device according to the present invention.  
         [0016]    [0016]FIG. 2 is a side view of a window motor and gear box forming part of the closure system of FIG. 1.  
         [0017]    [0017]FIG. 3 is a side view of the device according to the present invention.  
         [0018]    [0018]FIG. 4 is an end view of the window motor, gear box and device in use.  
         [0019]    [0019]FIGS. 5 and 6 are further views of FIG. 2.  
         [0020]    [0020]FIG. 7 is a schematic block diagram of the device. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]    With reference to FIG. 1A where is shown a vehicle  10  having a door  12  with a window aperture  14 . An aperture closure in the form of a window glass  16  is moveable vertically to open and close the window aperture  14 . A window regulator shown generally as  18  includes a window motor  20  and a gearbox  22 .  
         [0022]    [0022]FIG. 1B illustrates a motor  20  and gearbox  22  fitted to a regulator having a single lift track  23 .  
         [0023]    Referring now to FIGS. 2, 3,  4  and  7 , the motor  20  and gearbox  22  are mounted to a fixed door panel  70 , such as a door module (or carrier plate), via a mount of which this embodiment comprises a printed circuit board (PCB) device  30  mounted intermediate the gearbox  22  and the panel  70  so that any loads induced between the gearbox  22  and the panel  70  are transmitted through the PCB device  30 .  
         [0024]    In this embodiment, of the gearbox  22  is mounted on the PCB device  30  by way of three pins  58 ,  60  and  62  (not shown) being secured through apertures  64 ,  66  and  68  of gearbox  22  and apertures  32 ,  34  and  36  of the PCB device  30 . The device  30  is mounted on the panel  70  by two pins  56  interconnecting apertures  24  and  26  on the device with corresponding apertures on the panel (only aperture  62  being visible in the Figures).  
         [0025]    It can be seen from FIG. 3, in this embodiment the PCB device  30  has a pentagonal shape with a large central circular hole provided therein. The hole enables an output shaft (not shown) from the gearbox to pass through the PCB device  30  to drive the remainder of the window regulator system  18 . In this embodiment, pairs of adjacent strain gauges are provided proximate mounting apertures  24  and  26 , although in other embodiments strain gauges may be provided in alternative locations, such as adjacent one or more of apertures  32 ,  34 , and  36 . However, it will be apparent that the invention in its simplest form requires only a single strain gauge.  
         [0026]    The strain gauges are preferably disposed on the PCB device  30  so as to maximize their response to the forces induced in the plane of the device  30  itself. The central hole in the device assists in achieving this, as does providing the apertures  24 ,  26 ,  32 ,  34 ,  36  and strain gauges proximate the periphery of the PCB device  30 . In this embodiment, strain gauges  38   a  and  40   a  are positioned perpendicular to adjacent strain gauges  38   b  and  40   b , thus enabling the forces to be resolved in any direction. In addition, the provision of at least two strain gauges means that differing ratios of strain may be applied to, and be measured by, each gauge. In turn, an arrangement of two or more strain gauges enables torque loads applied by the motor to be at least partially distinguished from extraneous forces to which the PCB device is subjected, for example. This aspect of the invention is discussed in greater detail below.  
         [0027]    The strain gauges  38   a ,  38   b ,  40   a  and  40   b  are printed on to substrate  31  of the PCB device  30  using a known PCB manufacturing technique such as photo deposition or photo etching. Hitherto, in similar applications discrete strain gauges have required gluing onto the member being strained plus subsequent electrical connections to be carried out by hand or on high capital cost automated equipment. Therefore, the aforesaid technique represents a significant cost saving. The shape, thickness and material of the substrate  31  are such that a sufficiently linear response is obtained from the strain gauges and the device  30  has sufficient strength to function as intended. Examples of suitable substrate materials are glass fibre and Paxolyn.  
         [0028]    In a preferred embodiment, further components may be mounted or printed on the device  30  such as a microprocessor controller  50 , signal conditioning components (not shown), output controls or relays (not shown) and temperature compensation circuitry  80 , vehicle connectors  52  and a motor connector  54  as well as general components such as resistors, capacitors, transistors, diodes and inductors, all of which may form a control circuit for the motor  20  when operated in conjunction with the strain gauges. By doing this, the control circuit for the window regulator becomes integrated with the whole sub-assembly, reducing the overall part count and hence reducing the cost of manufacture of the system still further.  
         [0029]    In one class of embodiment, a standard motor  20  is used, and an interface is provided on the device between the control circuit and the motor, but in other embodiments, a specific interface may be provided on the motor  20  to allow a simple connection to the control circuit. To provide mechanical and environmental protection, the device  30  and any associated components are preferably encapsulated by a suitable resin material, or within a suitable enclosure (not shown).  
         [0030]    Optionally, the PCB device  30  may also incorporate sensors  82  to determine the rotational position of the output shaft so as to provide feedback to the controller  50  about the position of the window  16 .  
         [0031]    Referring in particular to FIG. 7, in use, a vehicle user with the vehicle ignition  84  switched on presses a window regulator switch  86  cause motor  20  to raise the window. If no obstruction is encountered, the window will fully close. An input from the positional sensors  82  preferably determines the position at which the anti-trap system may be overridden to enable the window to overcome the resistance of the seals at the top of the opening. In one class of embodiments, the positional sensors subsequently determine when the window is fully closed, thereby overriding the signal from the window regulator switch and preventing the motor  20  stalling. However, it is more common for the motor  20  to be allowed to stall as this provides the best seal. A protection circuit (not shown) is thus preferably provided to switch the motor off before overheating thereof occurs in this preferred embodiment.  
         [0032]    If an obstruction is encountered during the raising of the window, this causes one or more of strain gauges ( 38   a ,  38   b ,  40   a ,  40   b ) to be more or less strained than would be the case were an obstruction not present. Under strain their electrical resistance changes and this change in resistance can be related to the amount of strain.  
         [0033]    This change in resistance is proportional to the torque induced by the resistance to rotation of the motor  20 . Once a predetermined current value is reached, the controller signals a cut-off of power being supplied to motor  20  thereby preventing injury or damage to the person or object causing the obstruction. Only once the obstruction is removed (and typically once the window is lowered by a predetermined amount such as 250 mm) can the vehicle window  16  be raised again.  
         [0034]    In a particularly preferred embodiment, the device is arranged such that it is possible to at least partially distinguish the forces applied to the closure by the motor  20  (and the resultant reaction force between the motor and panel) from acceleration forces applied to the closure  16  as a result of the accelerations of the closure system (e.g. caused by the vehicle driving over rough terrain).  
         [0035]    Referring to FIGS. 5 and 6, it can be seen that first and second mounting apertures form part of a load reaction path between the motor  20  and the vehicle door panel  70 , and that between them they constrain the motor  20  within the door.  
         [0036]    The mounting apertures  24  and  26  are positioned at distance 2R from each other and the geometrical position of the centre-of-gravity CG of the motor/gearbox is also known.  
         [0037]    Consideration of FIG. 6 shows that resultant forces S1 and S2 act about mounting apertures  24  and  26 .  
         [0038]    An output torque T from the motor acts clockwise around the motor output shaft when the window is being closed and, with the vehicle  10  stationary, is a function of output force f.  
         [0039]    The weight of the gearbox and window motor acts through the center-of-gravity CG. With the vehicle  10  stationary the force M at CG is equivalent to the combined weight of the motor  20  and gearbox  22 . However, with the vehicle moving over rough terrain the force M will vary. It should be noted that CG is located horizontally by distance x from mounting aperture  24  and vertically from mounting aperture by distance z.  
         [0040]    Consideration of FIG. 6 shows that the forces S1 and S2 can be resolved in the x and y directions and become S1x, S1z, S2x and S2z. The output torque T of the motor can be considered to be a tangential force Ft acting at a radius r equivalent to the pitch circle diameter of a drum or pinion and, for convenience, this has been shown to be parallel to the z axis.  
         [0041]    Note that the analysis below is more complicated where the sensors and output shaft are not in line, and/or the forces act at some other angle, but it may be demonstrated that the same principles apply.  
         [0042]    Consideration of the above shows that several equations can be written, which express the situation at steady state i.e. with the vehicle  10  stationary and the window closing at a constant speed.  
         [0043]    Given that we do not know the directions of S1 and S2 merely their magnitudes then, by Pythagoras:  
         [0044]    S1x 2 +S1z 2 =S1 2  and S2x 2 +S2z 2 =S2 2    
         [0045]    Since we have conveniently defined Ft parallel to z axis and M acting vertically downwards, also parallel to the z axis then Ft x=0 and Ft z=Ft.  
         [0046]    Furthermore Fmx=0 and Fmz=M.  
         [0047]    Resolving in x and z we have the summations:  
         [0048]    x=0, z=0  
         [0049]    thus  
         [0050]    S1x+s2x=0, S1z+S2z=Ft−M  
         [0051]    And taking moments about S1  
         [0052]    S2z.2R+FT.(R+r)=M.x  
         [0053]    Collecting Terms  
         [0054]    S2z=Ft.(R+r)/2.R−M.x/2.R  
         [0055]    of which R, r &amp; x are all known and constant for a given application.  
         [0056]    S2z=Ft.k1−M.k2  
         [0057]    Where the constants k1=(R+r)/2.R&amp;k2=x/2.R;  
         [0058]    Thus  
         [0059]    S1z=Ft−M−S2z  
         [0060]    S1z=Ft−M−Ft.(R+r)/2.R−M.x/2.R  
         [0061]    Collecting Terms  
         [0062]    S1x=Ft−Ft.(R+r)/2.R−M−M.x/2.r  
         [0063]    S1z=Ft(1.(R+r)/2.R)−M(M1−x/2.R)  
         [0064]    But k1=(R+r)/2.r &amp; K2=x/2.R, so  
         [0065]    S1z=Ft (1−k1)−M(1−k2)  
         [0066]    following which  
         [0067]    Thus S2=Ft.k1−M.k2  
         [0068]    and  
         [0069]    S1=Ft(1−k1)−M(1−k2)  
         [0070]    S1 and S2 from the output from the mounting apertures  24  and  26 , k1 and k2 being constant, we now have two equations and two unknowns (Ft and M) and therefore can solve for Ft and M.  
         [0071]    This solution allows comparison of the motor/gearbox effective weight M and the known pre-measured value of the motor/gearbox weight. This comparison gives an instantaneous value for the vertical g-forces applied to the window motor and therefore the adjacent window glass and permits greater discrimination of the system loads resulting from the vehicle movement from those associated with a trapped object or body part.  
         [0072]    Thus the above system, by comparing the output S1 and S2 from the mounting apertures  24  and  26 , the proportion of the measured output due to vertical acceleration and that due to an object trapped may be distinguished arithmetically and thus a better definition of actual trap force (as opposed to apparent trap force) may be obtained. As such it is possible to largely eliminate interference with the true trap force signal caused by vibration and/or accelerations with a large vertical component. The present invention achieves this in a particular cost effective manner as a minimum of components are required since the strain gauges  38   a ,  38   b ,  40   a  and  40   b  are provided integrally on the PCB device  30 , and also measure the parameters which can be used to determine true trap force from apparent trap force.  
         [0073]    As a result of improved sensitivity of the system to objects being trapped, lower force thresholds may be specified and therefore more rapid reaction may be obtained both of which leads to a reduction in the overall trap force experienced by the person or object.  
         [0074]    The system also reduces the likelihood of false trap signals and hence false reopening of the window, thus reducing the possibility of distraction and annoyance to occupants of the vehicle.  
         [0075]    Once the window is virtually closed such that any gap between the window glass and window aperture is sufficiently small to not allow entry of a small body part such as a finger, then the anti-squeeze requirement is no longer necessary. Thus when the window glass reaches such a position this position can be indicated by a proximity sensor, micro switch, shaft positional sensors  82  or the like which would indicate to the controller  50  of the window that anti-squeeze is no longer required for the final closing of the window.  
         [0076]    It is envisaged that the present invention could be used in a variety of applications, such as automotive windows and other partitions moving in a primarily vertical direction. However, the principles outlined above would be applicable to other types of closure where the motor may be so mounted as to be subject to the disturbing forces in the same manner as the closure being operated by that motor. Further applications include vehicular sun roofs, transverse and longitudinal sliding doors as typically used for corridor and compartment closures in trains and aircraft, and other types of sliding partition on ships and other marine vehicles.  
         [0077]    The aforementioned description is exemplary rather that limiting. Many modifications and variations of the present invention are possible in light of the above teachings. The preferred embodiments of this invention have been disclosed. However, one of ordinary skill in the art would recognize that certain modifications would come within the scope of this invention. Hence, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described. For this reason the following claims should be studied to determine the true scope and content of this invention.